116 DESCRIPTION OF THE PLATES. 



tozpa. This opinion, however, is incorrect, as 

 may be seen in the accompanying drawings, 

 where figures are given representing all the 

 details of the developement of the true sper- 

 matozoa. These are all produced from cells, 

 whereas the entozoa under consideration are 

 never seen within cells, but are in all cases 

 generally seen floating free in the seminal ves- 

 sels. These filaria have only been seen, so far 

 as I am aware, in Amphipoda and Isopoda. If 

 they are spermatozoa, they must be produced 

 from cells ; and from what has been stated in the 

 text, it will be seen that in all the Crustacea, 

 these cells, before producing the spermatozoa, 

 undergo several metamorphoses; and that the 

 final changes take place in the spermatheca of 

 the female, where the seminal animalcules are 

 produced. In Amphipoda, and Isopoda, where 

 these supposed filaria exist, we always find them 

 high up in the testicle, and not occasionally, but 

 in great numbers. In the tertiary seminal cells 

 also, which are floating about among them, not 

 the slightest vestige of the worm can be ob- 

 served. I am inclined to suppose, therefore, that 

 these thread-like worms, supposed by Kolliker 

 to be spermatozoa, are only parasites. 



PLATE IV. Fig. 2. Representation of a primary germinal cell pro- 

 jecting from the wall of the seminal tube. It 

 has just burst, and the young secondary cells 

 are escaping and descending the tube ; during 

 the descent they increase in size, from their nu- 

 cleus throwing off nucleoli, the latter forming the 

 tertiary generation. In this figure it will be ob- 

 served that the cell walls of the parent are quite 

 smooth and unbroken, so that in all probability 

 the young arise from that portion of the cell at- 

 tached to the seminal tube. 



Fig. 3. Is a small quantity of the fluid from the sperma- 

 theca of the female crab, showing the tertiary 

 or spermatozoa! cells after they have burst from 



