106 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



(ex. 2 spines. fex. 1 seta, 



ap. 1 spine, 1 seta. Inner ramus < ap. 2 spines, 



in. 4 spines. ( in. 2 sette. 



The spines are serrulate and the sette very plumose. Fifth foot 

 two-jointed, basal joint longer than wide, with a series of small teeth 

 and a long seta, apical joint with three plumose setse. Color bluish 

 or banded, the antennte especially banded on the fifth to sixth and 

 twelfth to fourteenth joints. 



* Cyclops sigiiatu.s var. coronatus. 



Plate XV, Figs. 1-4. 



First segment of thorax long, its length to that of the entire thorax 

 about as 1 : 1.50. Last segment of antennae with the proximal portion 

 of its hyaline plate coarsely serrate. Caudal stylets short, ciliated 

 internally, length to width as 1.25 : 1. Second segment of antennules 

 short. Inner apical seta of stylets one-third longer. Color marked. 



* Cyclops signatus var. tenuicornis. 



Plates XV, Figs. 5-7; XX, Figs, 1-7; XXXIII, Figs. 1, 2. 



First segment of thorax shorter, its length to that of the entire 

 thorax as 1:1.9. L:ist segment of antennsp. with unserrated lamella. 

 Caudal stylets longer, length to width as 2.1:1, inner aspect not 

 ciliated. Outer apical seta half as long as inner. Second segment of 

 antennules longer. Color variable but always banded or splotched. 

 It is also generally true that the ovisacs in the present variety are 

 more strongly divaricate than in the variety coronatus. 



Schmeil also finds differences in the form of the receptaculum and 

 sexual elements. 



Over against the above differences must be set the close agreement 

 in the armature of the feet and the fact that the late stages of coronatus 

 remain to be described while it is always associated with C. temdcorms, 

 generally in greater numbers. The greater hairiness and stronger 

 serrations of G. coronatus are characters suggestive of advanced age, 

 as has been observed in other species. G. tenuicornis is frequently 

 found without G. coronatus, but the reverse has not been found true in 

 our experience. Finally attempts at experimental rearing of coronatus 

 from tenuicornis have been made, and, while some possible sources of 

 error unfortunately crept in, yet I am morally convinced that the ap- 

 parent transformation was genuine. 



Dr. Schmeil discusses this question at length without adding any- 

 thing to the evidence. He adduces the differences in structure, 

 though he fails to find anything but such as consist in altered pro- 

 portions of structures common to both. He claims that embryos of 



