THE OSTRACODA 8oi 



The vertical distribution of these forms has not been fully worked 

 out. Various species of Candona, Ilyocypris, as well as Cypridopsis 

 vidua and Cyclocypris laevis have been found at depths of at least 

 300 meters, while a few have been reported from depths of fully 

 2500 meters. 



The constancy of color, form, and size of most of these species is 

 still an open question, and yet requires much careful work. Be- 

 cause of differences in methods of measuring and the chance that 

 undeveloped or sexually immature individuals become described, 

 it is certain that there exist many discrepancies as to published 

 descriptions, and therefore of reports on distribution. 



Despite these discrepancies and uncertainties, it is likely that 

 local varieties exist in many quite restricted areas, that in many 

 cases are so far divergent that one would be disposed to ascribe 

 them to different species. On this account, if for no other, it is 

 advisable to be very careful concerning the establishment of new 

 species. In all cases the appendages should be very critically 

 examined, and if these show differences and the shells are constant 

 in general markings and form, then only should a new species 

 be created. Of course, very exact and minute descriptions are 

 indispensable. 



The distribution of Ostracoda seems to be both actively and 

 passively brought about. The creeping forms may be said to be 

 actively distributed, while the free-swimming forms are passively 

 distributed. Those that creep must actively exert themselves if 

 in deep water, often against the force of the stream, to prevent 

 themselves from being buried in the mud. Passively, the swim- 

 mers may be distributed by high water or by direct means of 

 transport. The amount of water is of more consequence than the 

 flow of water. Even though the amount of water is great, they 

 still can remain in the place of their temporary abode, while in 

 brooks or rivers they are carried away by the force of the current, 

 and may become lost. In rainy seasons, therefore, the natural 

 increase may be very scanty, while in drier periods many indi- 

 viduals of both sexes find one another, and the eggs deposited always 

 have a sufficient opportunity of finding necessary moisture for 

 development. 



