30 



Vertebrates. They are also entrapped and digested by the aquatic 

 plants known as Bladderworts. But the most important fact for us 

 in this connection is that they form a large part of the food of nearly 

 all young fishes. Some species of fish, indeed, feed principally upon 

 Entomostraca during the whole of their lives. It is evident, there- 

 fore, that any rational system of fish-culture must take cognisance of 

 the habits and needs of the Entomostraca. 



From the point of view of experimental biology the fresh-water 

 Entomostraca offer a wide field for research, and one, too, which has 

 scarcely been touched. Their commonness in all parts of the 

 country, their transparency, the ease with which they can be isolated 

 and reared under all sorts of conditions, such are some of the facts 

 which mark out the Entomostraca as particularly well fitted for 

 observation in connection with even the most fundamental biological 

 problems of the day. It was in a water-flea that Metschnikoff first 

 saw the leucocytes (or phagocytes) trying to get rid of disease germs 

 by swallowing them, and was so led to his epoch-making discovery 

 of the part played by these minute amoeboid corpuscles in the animal 

 body. Weismann has also to some extent made use of the Ento- 

 mostraca for experimental work in relation to heredity and variation. 



Apart from such first-class biological work, there is a great deal 

 that could be profitably undertaken by amateurs in connection with 

 the British Entomostracan fauna. We badly want detailed studies 

 on local faunas, on the seasonal distribution and variation of 

 the different species, on the faunas of various types of ponds, on 

 the food of the most abundant forms, and many similar subjects. 

 And it may not be superfluous to point out that incidentally such 

 work would certainly lead to the discovery of many species new 

 to this country and perhaps to science. 



In conclusion, I need scarcely say that if any members of this 

 Society should - be tempted to take up the study of the fresh-water 

 Entomostraca, it will be a pleasure to me to give them all the 

 assistance that lies in my power. 



