462 M. Louise Nichols. 



which stained intensely with gentian violet. It seems probable that 

 this represents the head, the pale fibres the tail. (Text Fig. 2.) 



Copepoda. McClendon (1907) describes the spermatozoon as very 

 similar to those of the Cirripedia. 



Malacostraca. Arthrostraca (Edriophthalmata). Those which 

 have been studied possess the flagellate type of spermatozoon. The 

 head and tail are sharply marked off, although sometimes no middle- 

 piece can be distinguished. Relations of size and position between 

 head and tail differ somewhat in the members of the group. A 

 simple rounded head followed by a tail of moderate length, and in 

 Talorchestia by a middle-piece, characterize the ximphipoda, while 

 in the Isopoda both head and tail are elongated, the latter excessively 

 so. The head and tail also, instead of joining in a straight line as 

 is the case with the Amphipoda, form wdth each other an acute 

 angle, as Gilson (1886) has described it, much like the handle of 

 a whip and its lash. The general appearance of the spermatozoa 

 resembles that of the Cirripedia. (Text Figs. 3, -4.) 



Thoracostraca ( Podophthahnata) . The spermatozoon of Mysis as 

 described by Gilson (1886) is very like that of the Cirripedia and 

 the Isopoda, the head and tail occupying similar relative positions, 

 but that of Squilla is quite different, seems indeed to forecast the 

 spermatozoon of the Decapoda. It is spherical in shape, the greater 

 part of the cell consisting of a colorless vesicle filled with hyaline 

 substance, while the only portion staining with methyl green is a 

 button- or lens-?haped body at one pole of the sphere. (Text Figs. 

 5, 6.) 



Grobben (1900), Koltzoft" and others have shown for the Decapoda 

 that the more nearly related adult members are, the more nearly 

 alike is the structure of the spermatozoa. Koltzoff (1906) especially 

 has worked out this subject with some care and has outlined a 

 genealogy of the Decapoda based on this feature. 



The characteristic most prominent in the Decapod spermatozoon 

 is the development of a resistant capsule in the region of the tail 

 (S. vesiculifera of Koltzoff). In the lower forms this is repre- 

 sented by a spine-like projection (S. anacantha). (Text Fig. 7 ) 

 In the higher forms it is more vesicular in shape and in the region 



