272 THE GENERATIVE OEGANS OF THE OYSTER. 



serve only as a provisional connection between tlie developing 

 spermatozoa and tlie wall of tlie follicle. The former cell grows 

 rapidly, and the nucleus subdivides rapidly and repeatedly until a 

 large cell is formed 25 — 30 /n in diameter, containing 40 — 50 nuclei. 

 Each nucleus is about 4 ^ in length. At this stage the whole 

 structure looks somewhat like a club (PI. XXIII, fig. 4), of which 

 the swollen part is formed by the large multinucleated cell just 

 described, and the handle is formed by the other derivative of the 

 primitive cell. At this stage the multinuclear cell becomes separated 

 from its peduncle. Its nuclei continue to subdivide and become 

 darker and more opaque. Finally the mother-cell becomes entirely 

 developed into spermatozoa derived from the sub-divided nucleus, 

 but one cannot explain precisely the steps by which the smallest 

 nuclei are transformed into spermatozoa. 



The Physiology op Geneeation in the Oyster. 



Numerous researches have been made with the view of determining 

 whether the oyster is a functional hermaphrodite, having the power 

 of occasionally or generally fertilising its own ova, or whether it is 

 physiologically unisexual whilstanatomically hermaphrodite. Davaine, 

 de Lacaze Duthiers, and P. J. Van Beneden pronounced in favour 

 of the former view, that the oyster is, potentially at least, a 

 functional hermaphrodite, but subsequent investigators have in- 

 clined more and more towards the latter view. Dr. Hoek's researches 

 lead him to the conclusion that, so far from being a functional herma- 

 phrodite, the oyster is a unisexual animal at the moment when it 

 performs the act of generation. He continues : 



"It goes without saying, and should not be forgotten, that it is 

 much more difficult to arrive at a certain result in this part of my 

 researches than in the anatomical part. In the latter direct obser- 

 vation is possible, but in the former it is only possible within certain 

 limits. One is obliged, indeed, to make observations from the very 

 first, but one has afterwards to draw conclusions from them, and 

 then everything depends on the greater or less importance which 

 one attributes to each fact observed. A multitude of observations 

 may give more solid grounds for one's conclusion, but cannot exclude 

 the possibility of a fault in reasoning. 



" The number of oysters examined was not very large. I call 

 ' examined ' those only which gave me satisfactory preparations and 

 in whicb I could judge with mathematical certainty the condition 

 of the generative organ at the moment of opening. Adult oysters 

 (three years old or more) opened during the breeding season do not 



