28o 



CALKINS. 



[Vol. XI. 



These differences can best be seen, perhaps, by the aid of 

 diagrams. If «, by c, d, etc., represent consecutive chromatin 

 elements in the monospirem, the following series can be 

 obtained, in which I indicates the composition of the Viercr- 

 griippen, II the first division, and III the second division : 



Ascarls 



CBrauex "93) 



nr 



© © 



© 



Copepods 



(Haecker '93) 



n 



III 



© © 



® ® 



I 



a a 



© 



Pyrrhocoris 



tKenking '90 



iir 



© © 

 ® ® 



Lumbricus 



III 



© © 



According to this schematic arrangement, the Vierergruppeiiy 

 which, in most cases, consist of two contiguous elements (a and 

 b) doubled, in Lumbricus consist of the element a doubled, and 

 united with any other element, x, also doubled. In this case 

 the end result is the same as in Pyrrhocoris or in the copepods, 

 but the method of arriving at it is different. 



The process, as in Lumbricus, is carried a step further in 

 Caloptcjius, where, according to Wilcox ('95), there is no pre- 

 liminary doubling of the spirem ; and, since there is here a 

 union of the spirem segments as in Lumbricus, the elements of 



the Vierergruppen would be indicated thus : , x and y repre- 

 senting any other chromatin segment than a and b. 



The results obtained in Lumbricus may, therefore, serve as a 

 link in the chain, the extremes of which are represented by the 

 views of Brauer and Wilcox. 



