466 PARASITES OF ANIMALS 



handles of the hooks, and they are also very frequently directed 

 into the transverse muscles of the skin. In Gyrodactylus cras- 

 siusculus we find a protrusor penis and retractor palparum 

 medius. (/.) Except in the case of G. elegans, four so-called 

 eye- spots are observed at the anterior extremity of all Gyro- 

 dactyli. As Siebold sayp, they answer the purpose of light- 

 refracting organs. The palpi, which in G. crassiusculus are 

 seen to contain muscular bundles, appear to be retractile touch- 

 organs, extending more or less prominently forward. (g.) 

 Observations in regard to the alimentary canal are at present 

 incomplete, for only in the case of G. cochlea did I find a 

 single gullet demonstrable, (h.) Gyrodactylus becomes sexu- 

 ally developed, and cannot be regarded merely as a kind of 

 ' nurse/ " 



So much for Wedl, whose views I have elsewhere recorded 

 at great length. The genetic relations subsisting amongst the 

 Gyrodactyles have given rise to much controversy. Observing 

 the singular mode of reproduction in G. elegans, Von Siebold 

 arrived at the conclusion that Gyrodactyles in general were 

 only nurse-forms of some higher organism, and he pointed 

 out, with undeniable accuracy, all the birth-stages of the young 

 one as it apparently pullulated within the parent and sub- 

 sequently emerged an almost perfect Gyrodactyle. Von Siebold 

 also remarked that the so-called " daughter," at the time of 

 birth, nearly equalled the " parent " in respect of size, whilst, 

 moreover, it contained within its interior another very young 

 Gyrodactyle, or, in other words, a " grand-daughter." Van 

 Beneden interpreted these facts very differently. I have myself 

 noticed the second generation, or daughter, to contain in its 

 interior evidences of a third generation. This I observed in 

 specimens obtained from the tails of Gasterostei caught in the 

 Serpentine, Regent's Park. Indications of the third progeny 

 were seen whilst the daughter still resided within the body of 

 the nurse-parent, and the so-called grand-daughter became 

 much larger immediately after birth. In one instance the 

 " daughter " commenced showing herself by a slight bulging 

 at the centre of the parent's body, whilst the integument of 

 the latter yielded on all sides of the bud-like projection, and in 

 such a manner as to convey the idea of a vaginal opening. 

 There was an evident struggle on the part of the young one to 

 free itself from the so-called parent envelope, but the tissues 

 showed no signs of injury. On partial protrusion it was seen 



