434 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



After lying in the spermatheca for some time, the wall of 

 the secondary cell becomes so thin that it bursts, and allows 

 the young cells to escape. These tertiary cells contain, and 

 are, the formative cells of the spermatozoa. In the higher 

 Crustacea, Brachyura, they each contain one or more sperma- 

 tozoa, in the Macroura one only. The spermatozoal cells are 

 nucleated when they first burst from the secondary cells, and 

 shortly the head of the spermatozoa is found to correspond to 

 the nucleus. 



The seminal fluid in all the species of Macroura is very 

 peculiar, the tertiary cells being in all cases armed with three 

 long slender setae.* They are oblong, and dilated at the 

 armed extremity. They are developed singly within their 

 parent cells ; sometimes, however, two may be observed in 

 one cell. These parent or secondary cells are oblong, and 

 bulge slightly in the middle. After they have remained for 

 some time in the spindle-shaped caeca (Galathed), the three 

 setae of the tertiary cell expand, and the cells begin their 

 descent. In the progress downwards, the unarmed extremity 

 acquires a small nucleated spot, and in many instances small 

 spherical cells are thrown off from this, which are quaternary, 

 and probably spermatozoal cells. In the cuirassed and digging 

 Macroura these tertiary cells are all armed with three setae, 

 many times longer than the body of the cell. In the prawn 

 these setae are short and truncated. 



Throughout the whole course of the lower part of the 

 seminal tube there may be observed during the active state 

 of the gland, and while the seminal cells are being produced, 

 a large quantity of albuminous matter in small irregular 

 masses floating among the cells in an aqueous fluid. I am 

 induced to believe that the cells derive their nourishment 

 from this matter. 



In the upper part of the tube, where the cells are small 



* Von Siebold in Miiller's Archiv, 1836. 



