Protozoa (1)1(1 Ixotifcrn at Havana, III. 379 



86. B. dorcas Gosse. 



This is a winter species, as the records of both years show. 

 It was found in towings from the Illinois Kiver and from all 

 the various lakes in which collections were made, from 

 December to April, with a few scattering occurrences just 

 before and after this period, becoming very abundant in 

 April. 



Like the preceding species, this one was found only in 

 towings, and is recognized as a pelagic form. 



87. B. dorcas spinosus Wierz. ('91). 



But few specimens of this variety were found. It occurred 

 in towings from the Illinois liiver and Quiver Lake during 

 May, 1894, and in towings from the river and Thompson's 

 Lake taken in January, March, and May, 1895. This indi- 

 cates a seasonal history like that of the typical form. 



88. B. punctatus Hempel ('9()). 



This was moderately common, and appeared from June to 

 September. It occurred only in the open water, and was 

 taken in most of the waters studied. 



I have had the opportunity to study living examples of this 

 rotifer since the publication of my description ('96), which 

 was drawn up from dead specimens somewhat inflated by 

 the preserving tiuid, and is consequently not as accurate as 

 it might be. I find that in the live specimens the dorso- 

 ventral diameter is less than was at first supposed, the 

 rotifer being flatter than the illustration represents it. 



89. B. urceolaris Ehkbg. 



This also seems to l)e a winter species, occurring from 

 January to April. It was found only the second year, in 

 towings from the river and from all the lakes studied except 

 Phelps Lake, and though usually not very common, it was 

 very abundant in Thompson's Lake in March. 



90. B. rubens Ehrbg. 



This species occurred from December to March in small 

 numbers in towings from the river and from all the lakes l)ut 



