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In June, 1895, when Apus was first observed, some of this species were also seen, but none taken. Upon a subsequent visit they were found to have disappeared. In 1896 they occurred literally by millions in the pool north of De Witt, and quite a number were taken. Subsequently they were found in various grassy pools some distance north, but not a single one was taken in the draw previously mentioned. Egg sacs were observed in this and the above named species.
One species of Branchinecta was also taken. These have no carapace and are quite different in appearance from the preceding. Out of the hundreds of Apus and large numbers of Eulimnadia and Estheria only five or six individuals of this variety were found, although diligently searched for. These were, in life, of a pale green color with carmine gonopoda, but fade quickly when placed in preservative.
None of the species of Phyllopoda which occur in the west have been exhaustively studied, and those belonging to the Eulimnadia it is difficult to get identified with certainty. There is an opportunity, therefore, to find out many things about these short-lived and interesting creatures and discover facts pertaining to their life history, still obscure, which would be of great scientific interest.
The writers will be pleased to receive any information concerning the occurrence of Phyllopoda in other parts of the state.
CONTINUED BIOLOGICAL OBSERVATIONS.
HENRY BALDWIN WARD.
The wonderful advance given to scientific investigation by the work of the first naturalist who brought system and order into animal study was so great that students were long turned in the same direction and many of them were content to go no further. To most of them the mere discovery of some new animal was a matter of great importance, while its life, habits, and environment received little or no attention. The organism required simply a label before it should be laid away on the shelf of some museum as known. Nor was the mere study of anatomical detail much advance upon this standpoint. The information gained was isolated and unconnected with other facts that had been observed, and in the amassing of detail unity was lost sight of. Within the last few decades, however, there has been growing a desire to do more than to merely label a specimen or describe the details of its structure from some alcoholic material. It has come to have importance as a living thing, standing in close relations to other living things, influencing them and influenced by them; in other words, as a part of a whole which of itself must be studied.
There are two ways in which the student may attack the problem of biological relations just suggested. He may investigate the sum of all the relations which pertain to a specific animal or those which are connected with a specific location with its sum of living things. The first problem is usually beyond the possibilities of the observer who does not possess considerable means for traveling or collecting through the medium of others, and the second, so far as it concerns a larger area, requires equally extensive collecting and an amount of literature which is not accessi
ble to the majority of students. It is my desire here to call attention to a type of biological study which can be carried on in any locality and by any student with some hopes of being able to attain valuable results.
Some years ago Forbes called attention to the fact that within a small lake we have a microcosm, a world dependent upon itself. Within this area is produced the entire amount of the food which is consumed by the animal life that inhabits the lake. The changes that take place are constant and yet constitute but a narrow circle. No area of land could be found of at all the same size, which would present equal possibilities for life, and at the same time so closely circumscribed that the problem would be confined to the area itself.
The distribution of life within larger bodies of water has been the object of study to numerous investigators in the Old World, and in this country has been successfully prosecuted by Birge and Marsh in Wisconsin, Reighard in Michigan, Forbes in Illinois, and many others. Thanks to their researches we have learned much concerning the distribution of aquatic life from year to year, and from place to place. Into this subject, however, it is not my purpose to go in detail. The information already gained will be of great value in attacking another aspect of the question. In the smaller areas of land and water the conditions are less variable and the problem in so far simpler. From the study of these limited environments, we must hope to attain to a better understanding of the biological laws which govern the change of material from the inorganic to the organic through its long series of steps. Every observer can find within easy reach a small pond which will serve as the object of his study. To it he must devote his undivided attention, and if he would succeed it must be mastered. The mere examination of the life it contains at the single time affords little information of value; hardly more useful are sporadic observations. The student must collect systematically and regularly throughout the entire year, keeping such record of conditions that he may be able to compare time with time. These collections must also be brought together in
such a way that they represent accurately the amount of life contained in a given amount of water under the observed conditions. From these data the student may determine the total quantity. of living matter in the water at that time, and the relative amount of each different species. As the observations are extended he will be able to trace the rise and fall of a particular species, noting its first appearance and tracing it to its final disappearance. As thus gradually he records the history of the life in this microcosm it is evident that, continued long enough and carefully enough, he is recording the conditions which modify, which control the life itself.
Evidently, then, from what has been said, such studies have need of special apparatus, which must be at once permanent, portable, and precise. Hitherto in collecting material the investigator has made use of nets drawn vertically, horizontally, or obliquely through the water. They are, however, far from fulfilling any of the conditions satisfactorily, which have been set by investigators for such work. It was some years ago that in connection with more extended biological investigations on the Great Lakes the idea of a pump as a means of obtaining, from a specific point, an accurate quantity of water together with the life it contained, was first suggested to my mind and discussed with others. Since then the same idea has been carried into execution by others and the results obtained have been satisfactory. But of the apparatus thus far devised, it may be fairly said that its excessive weight and considerable cost renders it rather inaccessible to the ordinary investigator.
In view of this fact, when suggesting to one of my more advanced students a topic along this line for investigation, I outlined to him a plan for a smaller pump which would be at once inexpensive and easily portable and which I hoped would give results satisfactory in precision as well. The plan which was submitted to him was carried out with some modification of detail and has proved its value in actual work, as he will explain to you in the next paper.
A NEW PLANKTON PUMP.
No field of research is more inviting to the student of science than the one offered by the waters teeming with minute animal and plant life. Work in this interesting line of investigation has progressed slowly because of a want of adequate collecting apparatus, which, until quite recently, has been limited to two simple types, the net working vertically through the water and the one working horizontally or obliquely, both of which present serious disadvantages, prominent among which is the liability to damage and loss. These nets are of necessity made of very delicate fabric and must be operated in water where there are many obstacles to tear and destroy them. The finer qualities of bolting cloth, of which the better nets are made, cost from $6 to $8 per yard. To spend this amount for material, a day or two in constructing the net, and then in the first haul to catch a huge snag that destroys the net is neither a delightful nor an uncommon experience.
Secondly, it is impossible to determine with any degree of accuracy the volume of organisms actually present in a given quantity of water. This difficulty arises from two causes: First, the manipulation of the net is attended with such disturbance as frightens away many of the organisms; secondly, it is impossible with the net to measure the water filtered. It is evident that if we wish to ascertain the number of crustacea, for instance, that exist in a cubic foot of a certain water, we must first be able to get a cubic foot of the water; with the net we cannot do this, for even though we know the area of the net opening it is so constructed and operated as to push aside some of the water, so that the net does not filter the entire column of water through which