22 PLANKTON OF WINNEBAGO AND GREEN LAKES. 



Seligo says that S. pectinata occurs through the whole year with 

 a maximum in September. 



Voigt (Voigt '02 ) says that 8. pectinata is generally absent 

 in the summer months, but is found in the fall, winter, and 

 spring, while other species occur in the summer. 



Conochilus volvox Ehrenberg. 



Conochilus was found in Lake Winnebago in the summers of 

 1899 and 1901. In 1899 it reached its greatest numbers in the 

 last week in July. In 1900 I found the largest numbers July 

 9. In 1900 a few were found in October and November. I 

 have not found it in any of the collections from Green lake, 

 nor does it seem to be distributed very generally in other lakes. 

 In September, 1899, I found it in Birch lake, in June, 1900, 

 in Cedar lake, Washington county, in August, 1900, in Pelican 

 and the Eagle River lakes, and in August, 1901, in consider- 

 able numbers in one of the Clover Leaf lakes. While it is not 

 at all uncomimon in the summjer months, its distribution seems 

 to be somewhat erratic. 



Apstein finds a much longer period for Conochilus, but states 

 that it is irregular in its maximum period. 



Voigt (Voigt '02) states that the period for Conochilus vol- 

 vox extends from August to November, but other species of 

 Conocliilus may occur in the winter months. 



Diaptomus minutus Lilljeborg and sicilis Forbes. 



D. oregonensis does not occur in Green lake but its place is 

 taken by D. minutus and D. sicilis. In a former paper 

 (Marsh 7 9T) I discussed the annual distribution of these Diap- 

 tomi, and the curves given in Plate II, while they modify the 

 conclusions reached at that time, do not do so in any material 

 way. As in my former work, I did not in the counting dis- 

 tinguish between the two species, but, in every case, careful ex- 

 amination was made as to the presence of the two species. I 

 have very little to add to the statement already made (Marsh 

 '97, 193) in regard to the annual distribution of these two 

 species. D. minutus occurs in the months from July to Decem- 



