1865.] Hincks on Zoophytes : the History of their Development. 407 



is identified with the most philosophical views of the subject, desig- 

 nates the hody which gives origin to the generative elements, the Gono- 

 phore. For reasons with which we need not now trouble our readers, 

 we prefer the term Gono-zooid — reproductive zooid — the element, that 

 is, of the Zoophyte, whether fixed or free, which discharges the sexual 

 functions, the equivalent of the flower-bud in the plant. Throughout 

 the remainder of this paper we shall employ this term as thus defined, 

 though by doing so, we shall discharge some of the romantic flavour 

 from our story. 



With respect to the second point, the structural identity of the 

 nutritive and the sexual zooids, however different in external aspect, 

 we shall hope to make it apparent in the course of the sketch of the 

 reproductive history of the Zoophyte, which we shall now proceed to 

 give. 



We have already seen that in the case of the Hydra, as in that of 

 the plant, two distinct classes of bud are developed, the one concerned 

 in nutrition, the other in reproduction, and the same holds good of 

 the Hydroid Zoophyte. Besides its multitude of busy polypites collect- 

 ing food, and with no other function, bodies are met with at certain 

 seasons of peculiar structure, which exhibit a true sexual character, 

 and, as Quatrefages puts it, "a qui seuls revient le soin d'assurer la 

 propagation de l'espece." These reproductive buds present many 

 varieties, — they have their many forms and even colours, like the 

 flower and fruit of the plant, — and they differ yet further and more 

 remarkably in this, that while some of thetn continue permanently 

 attached to the stock, others, at a certain stage, become free. 

 The latter disguised by the locomotive organs, with which they are 

 furnished for the vagrant term of their existence, and long known to 

 the naturalist, apart from all their connections, are the Naked-eyed Me- 

 dusae, of authors (Plate i. fig. 2). We must not, however, draw too 

 broad a line of distinction between the fixed and the free reproductive 

 zooids. They are both portions of a series, through which indeed 

 "one increasing purpose runs," but also an identity of essential ele- 

 ments. 



The fixed sexual bud of the Zoophyte matures and discharges its 

 contents in situ. The free zooid, liberated from the parent stock, 

 bears with it the seed of new commonwealths, and colonizes distant 

 seas. 



Let us trace the history of these bodies. They are produced on 

 various parts of the Zoophyte. Sometimes they bud from the ordi- 

 nary polypite and form a kind of collar near the base of its tentacles 

 (Plate i. fig. 1). Sometimes they occur near the lower extremity of 

 the body, pullulating in opposite clusters (Plate i. fig. 6). 



In some cases, a partially-developed polypite, one in which 

 growth has been more or less arrested, supports the reproductive 

 zooids (Plate i. fig. 5). Sometimes the atrophy shows itself merely 

 in a reduced number of tentacles ; sometimes the arms disappear alto- 

 gether, as in the Hydractinia (Plate i. fig. 5) ; sometimes it sets in 

 only as the sexual buds approach maturity, and a greater drain takes 



