198 LECTUEES ON BIOLOGY 



is suspended, the arms become rudimentary, the larvae assume 

 the shape of a hemisphere, and recall only distantly the normal 

 Platens. 



Considerable sensation was caused not long ago by an observa- 

 tion made by Schmankewitsch in some of the lower crustaceans. 

 In the brine-pools on the coast of Istria is found a small 

 crustacean, the Brine-shrimp (Artemia salina). It is distin- 

 guished from its northern relative Branchipus, which occurs in 

 many districts of Germany in ponds and ditches, chiefly by the 

 smaller number of abdominal segments and certain other 

 characteristics. Schmankewitsch contended that by a gradual 

 sweetening of the water it is possible to transform Artemia into a 

 typical Branchipus, and further, that gradual increase in the 

 salinity transforms Artemia salina into a different species, Artemia 

 milhauseni, which is distinguished by a very short, thick, spineless 

 tail-lobe. Kecently the statements made by Schmankewitsch 

 have been contradicted, at any rate in this form, by the investi- 

 gations of Samter and Heymons. Nevertheless, it is certain and 

 this is the essential point that the change in the salinity of the 

 water undoubtedly brings about a radical change in Artemia 

 salina, even if it cannot transform it into a typical Branchipus 

 or Artemia milhauseni. 



Numerous observations of apiculturists and observers of ants 

 have made it clear that the variety of form in ants, bees, and 

 termites is mainly the result of an external factor, fcod. Thus, 

 if the queen of a bee-colony is dead and there is no royal brood, 

 the bees are able to transform ordinary worker-larvae into queens 

 by giving them suitable food. In bees we also seem to obtain 

 a deeper insight into the causes which determine the future sex 

 of the animals, for it is believed that the drones, i.e., male bees, 

 always develop from the unfertilized eggs of the queen, while 

 queens and workers always develop from the fertilized eggs. 



Numerous instances are known of the influence of food upon 

 higher animals. In tadpoles which are fed on vegetable matter 

 the intestines reach a length which exceeds that of the body 

 about seven times ; but if we feed the larvae exclusively on flesh 

 food the intestines become only half as long. Canaries fed with 

 cayenne pepper assume a reddish colour ; a course of hemp-seed 

 diet gives to bullfinches a black colour. The natives of the 



