213 WAGENERj ON GYRODACTYLUS ELEGAXS. 



liooks. Ill favorable cases indications of a third generation 

 even may be perceived within the second. 



From the foregoing observations it is obvious that Gyro- 

 dactylus produces at least one generation in the sexual way. 

 How the second and third embryo arise has not yet been 

 cleared up. 



[To these observations succeed some remarks upon the 

 question as to how the contained embryos of the second and 

 third generations arise, which, however, we omit for want of 

 space, merely stating the propositions, which appear to the 

 author to require elucidation. 



1. The second and third generations may arise like the first 



in which they are contained ; that is to say, in a sexual 

 manner. 



2. Or it may be that portions of the original vitellus or 



•uterine ovum from which the first generation was pro- 

 duced, remain over, which, even when contained in the 

 embryo, repeat its formation. 



3. Or the second and third generations are to be regarded as 



spores. 



For further information respecting Gyrodactylus, refer to : 



V. Nordmann. — ' Mikrographische Beitrage/ i. p. 106 ; Tab. 



X, figs. 1,2;^ Ann. d. Sc. Nat,' tom. xxx, pi. xix, fig. 7. 

 Creplin. — ' Ersch and Gruber's Encyclopadie,' xxxii, p. 301 ; 



Froriep, ' Neue Notizen,' viii, p. 84 ; Wiegmann's 



' Archiv,' (1839) p. 164. Bd. ii. 

 Dujardin. — ' Histoire naturelle des Helminthes,' p. 480. 

 V. Siebold. — ' Zeitschrift fiir Wissenschaft. Zoologie,' i, p. 



347. (1849). 

 Diesing. — ' Systema Helminthum,' i, p, 432, 641, 651 ; 



' Fitzungsherichte der Math. Naturw. Klasse der K . K. 



Akademie in Wien,' xxxii, p. 375, (1858). 

 Wagener. — ' Natuurkund Verhandeling.' Haarlem, xiii, p, 



51, 54. 

 Van Beneden. — ' Memoire couronne sur les Vers intestinaux/ 



p, 63. 

 Bradley C. L. — ' Journal of Proceedings of Linnean Society,' 



V, p. 209, (I860).] * - 



