148 



GENERAL ZOOLOGY 



geomet'rica (Fig. 74). Unless one should see it represented in 

 its natural environment, or actually find it there, the peculiar 

 slender form and the widely 

 separated groups of legs could 

 not be explained on the 

 ground of adaptation to its 

 environment. The artist has 

 shown the details of structure, 

 and also the general resem- 

 blance of the body and ap- 

 pendages to a portion of the 

 brown seaweed. The animal 

 is a little over a centimeter 

 long. The four flap-like ap- 

 pendages in the middle regions 

 . are gills. Caprella is 



composed of twenty 



somites. 





FIG. 74. Caprella. x 2 



Artemia. The genus Arte'mia is found in brackish water 

 (see larva, Fig. 78, p. 152). It is particularly interesting in 

 the light of experiments showing the direct influence of 

 the environment on an animal form. From 1871 to 1874 

 the Russian naturalist Schmankewitsch experimented with 

 Artemia. In one series of experiments he increased the 

 density of the brackish water in which they lived by add- 

 ing salt ; in another series he diluted the brackish water by 

 adding fresh water. After several generations of Artemia 

 had been produced under these conditions it was found that 



