DECAPODA. 



525 



are contained in spermatophores, the material of which is secreted 

 by the vasa deferentia (Grobben). The sperm from one side 

 may be carried in a single spermatophore, as in many Brachyura. 

 etc. In the crayfish (Astacus) the secretion hardens on coming 

 in contact with water into the chalky white substance which 

 may often be found on the under surface of the female. 



The spermatozoa have long been recognized as exceptional 

 in that they are without a vibratile flagellum, they are usually 

 beset with three or more diverging processes, and they are deprived 

 of the power of independent locomotion. Light has been thrown 

 on the function of these remarkable structures and the relation 

 of their parts to those of other spermatozoa, by Koltzoff (1. c.) 

 who has examined their development in particular cases. 



FIG. 322. Decapod spermatozoa, a, spermatozoon of Galathea squamifera (after Koltzotf). 

 1 head ; 2 neck, with processes ; 3 capsule ; c.a anterior centrosome ; c.p and c.p II anterior 

 and posterior division of posterior centrosome. b, spermatozoon of Astacus fluviatilis, 

 showing the capsule sunk in the head, c, the same, seen from above, and more highly 

 magnified (after Grobben). 



Fig. 322 a represents a spermatozoon of the Anomuran Galathea 

 squamifera. It consists of (1) a large head (represented below 

 in the figure), containing the nucleus ; (2) a neck, the constricted 

 part at the base of the head, containing the anterior centrosome 

 and produced into three long processes, which, though so rigid that 

 they can support the spermatozoon as on a tripod, are capable of 

 contraction, and at their tips at any rate are highly adhesive ; 



