294 



ROBERT CHAMIU-:KS, JR. 



this a case of interrelationship between C. parcus and C. Ameri- 

 can us. That this cannot he so is to be seen from the following: 

 I was fortunate enough to section the specimen when the chromo- 

 somes of its oviduct eggs were in the so-called "biserial arrange- 

 ment" and where the count is particularly easy. The presence 



o 



o 



' 



,. - 



h 













Nucleus of oviduct egg of Cyclops parcus, showing the three pairs of chromosomes 



in "biserial arrangement." 



of three pairs of chromosomes (see text figure) leaves no doubt 

 as to the identity of the specimen. 



The European Cycl. viridis has 12 chromosomes (Haecker, 

 Braun). 



Haecker ('97) described Cyclops brevicornis ( 'laus (viridis 

 J urine) which lie studied as being anywhere from 3.5 5 mm. in 

 length. The size mentioned indicates thai he was probably 

 working with var. gigas Claus. It is remarkable that he gives 

 the somatic chromosome number to be 24, although in the ovary 

 he describes the chromosomes as bivalent, being 12 in number. 



Braun ('09) also studied Cyclops viridis Jurine but not the 

 variety gigas. He gives the somatic number of chromosomes 

 for the typical species as 12. Unfortunately he does not mention 

 sizes except in stating that the species varies between 1.5 5.1 

 mm. in length. 



Schmeil ('92) gives the body length of the typical I European 

 viridis to be anywhere from 1.5-3.5 nun. 



Wolf ('05) places the average length at 2.2 mm. ( Mir American 

 parcus on the other hand is not more than half the average si/e 



