I860.] Hincks on Zoophytes : the History of their Development. 415 



closely investing the base of the proboscis, and their upper portion to 

 be furnished with a sucker-bearing fork, and he will have the sexual 

 polypite. As we have remarked elsewhere,* there is the closest resem- 

 blance between the two, the arms of both " exhibiting the same 

 number of opake-white patches, and in precisely the same positions." 

 The Gono-zooid of Clavatella is an ambulatory polypite, with the 

 simple circulatory system, and the eye-specks, which are needful to 

 it as a free being. 



Agassiz, in his great work on the ' Natural History of the United 

 States,' describes the fixed reproductive bud of a Hydroid (PJuzogeton 

 fusiformis, Agass.), f as being developed into a polypite, after com- 

 pleting its sexual functions, and he considers this the most direct evi- 

 dence thus far obtained of the structural identity of the two bodies. 

 (Vol. iv. p. 226.) Prof. Alhnan regards the phenomenon as abnormal ; 

 but even so, it is not the less important evidence. 



One other class of facts may be mentioned in this connection. In 

 some cases, at least, the Gono-zooid, after a term of free life, returns 

 to a stationary condition before the liberation of the ova. The locomo- 

 tive energy fails, the delicate swimming-bell is thrown back and turns 

 inside out (Plate ii. fig. 11), gradually it collapses and shrinks up 

 into a shapeless mass, hanging in this condition about the base of the 

 body, with the tentacles streaming behind it (Plate ii. fig. 12). The 

 disguise is now thrown aside, and the polypite remains, laden with 

 ova (a). It continues quiescent until they are discharged, and after 

 this fades away. 



Dujardin describes the Gono-zooid of a species of Staaridium, as 

 thus casting aside its locomotive apparatus when its course was nearly 

 rim, and resuming the sedentary habits of its tribe, and his observa- 

 tions have been confirmed by Mr. Holdsworth. We have seen the 

 same thing in the case of a Coryne and of the Podocoryne, and Mr. Peach 

 has reported to the like effect of the latter.^ We believe it to be the 

 normal course in these cases. 



* ' Anuals of Nat. Hist.' for Februaiy, 1861. 



t Plate ii. fig 10. 



% Vid. Ann. Nat. Hist. f2nd ser.) vol. xviii., 1856, p. 99. Mr. Peacli supposed 

 that in this ease the polypite was metamorphosed into the Medusoid. But there 

 can be little doubt that this was an error. From an examination of his figures and 

 description, we are convinced that lie had a species of Podocoryne before him, 

 closely allied to P. carnea, if not identical with it, the four leaf-like appendages 

 on which delicate arms were sometimes seen, being the attached Gono-zooids, and 

 the four filiform appendages, the tentacles, which are often few in number, on the 

 prolific polypites. In the case referred to in the text as having come under our 

 own observation, the Gono-zooid did not perish even after the liberation of the 

 ova and the disappearance of the peduncle. 



The remains of the swimming bell (pi. ii. fig. 12 b) sloughed away and the 

 bulbous bases of the tentacles (c) were fused into a single mass, of hemispherical 

 form, and orange colour, around which an ectodermal covering formed (pi. ii. fig. 13 c). 



The specimens continued free in this condition for a time, the arms being in 

 frequent motion. At last some of them became attached by the base, round the 

 edge of which a thin rim of transparent matter appeared, most of the arms withered 

 away, and in one or two instances an ascending shoot sprouted in the centre of the 

 orange disc (PI. ii. fig. 14). Further than this, we were unable to follow their 



