50 ENTOZOA. 



parental envelope closed in upon the opening, and all that remained 

 was a small cavity or sac, indicating the position recently occupied 

 by the " daughter " Gyrodactylus. Altogether, the process occu- 

 pied about five minutes from the commencement of the "budding" 

 to the closure of the assumed vaginal outlet. In this instance I 

 carefully compared the so-called "parent" with the "daughter," 

 but in regard to size I can scarcely aver that the former was the 

 larger of the two. The similarity of bulk is, perhaps, more 

 apparent than real, owing to the circumstance that the freed 

 young one rapidly extends itself and moves about in all directions, 

 whilst the parent as readily contracts, or " shuts up," so to speak, 

 thus appearing at a striking disadvantage. 



As I have before hinted, Yan Beneden demurs altogether to the 

 relational view of these creatures estabhshed by Von Siebold. He 

 does not admit the parent to be a kind of "nurse;" he does not 

 consider the primary young one to be a "daughter;" and, conse- 

 quently, he does not regard the embryo seen within the latter as a 

 "grand-daughter." Yan Beneden, whose words I translate lite- 

 rally, writes as follows :* — " According to our researches there 

 is here a false interpretation ; the little daughter is lodged within 

 the side of its pretended mother, and not in its interior ; instead 

 of being its mother, it is its sister ; there is a difference of shape, 

 because there is a difference of age ; the Gyrodactyles are vivipa- 

 rous, and as among the higher Trematodes the eggs are formed 

 one by one, one embryo is scarcely formed when another com- 

 mences its evolution, and the egg-deposition is effected even whilst 

 the embryo is being produced. The Gyrodactyles are therefore 

 viviparous worms which beget a single embryo at a time, as those 

 of the trematode group to which they are allied beget a single egg 

 at a time ; and before the first embryo is expelled another is already 

 partly developed. There, we believe, lies the correct interpreta- 

 tion of that phenomenon ; instead of a bud it is an embryo, which 

 has escaped from an egg. Here, therefore, we have no phenome- 



* " Memoire sui- les Vers Intestineaux." — Paris, 1868, p. 66. 



