Prof. Allman on the Hydroida. 7 



the axis of the bud ; it gradually elongates itself, and is to be- 

 come the manubrium of the medusoid. 



The four peripheral processes continue to elongate^ and are 

 soon seen to be dilated into bulb-like expansions at their extre- 

 mities. The bulbs increase in size, and come in contact by their 

 sides; while one of them, enlarging much more rapidly than the 

 other three, gives a marked preponderance to its side of the bud, 

 and makes the distal end of the bud appear as if obliquely trun- 

 cated. It then begins to extend itself beyond this distal end 

 into a thick hollow tentacle. 



In the mean time the four bulbs which had come in contact 

 have coalesced, and their cavities now communicate with one 

 another; but by the gradual enlargement of the distal end of 

 the bud the bulbous ends of the radiating canals are again drawn 

 away from one another ; the communication, however, between 

 their cavities is not thereby interrupted, but continues to be 

 maintained by a tubular elongation of their original points of 

 union ; and in this tube we now recognize the circular canal of 

 the medusoid. 



The cavity of the nectocalyx is still closed by the more ex- 

 ternal of the two laminae into which the ectoderm had originally 

 split at the distal end of the bud. In the final stage this lamina 

 becomes perforated in the centre, and forms the velum of the 

 medusoid; while the manubrium, previously imperforate, acquires 

 a mouth at its extremity. The solitary tentacle, too, has now 

 become elongated, and presents its characteristic moniliform 

 structure ; the nectocalyx rapidly contracts and expands with 

 vigorous systole and diastole ; and the medusoid at last hangs 

 upon its stalk, a true Steensti'upia, ready to break away from the 

 restraint of its fostering polype and enter upon an independent 

 existence. 



Besides the production of medusoid sexual buds, I have also 

 witnessed in Corymorpha nutans another process of reproduction, 

 very remarkable, but of whose exact significance I am unable to 

 speak with entire confidence. In a glass jar containing living 

 specimens of Corymorpha, which had been in my possession for 

 more than a fortnight, I observed attached here and there to the 

 surface of the glass minute oblong bodies, about \ a line in their 

 longer diameter, and | line in the shorter. They appeared to 

 be composed of a soft, minutely granular, white substance ; and 

 their interior was occupied by a very distinct cavity. They were 

 destitute of cilia, and were invested by an extremely delicate 

 membranous or mucous tube, quite structureless, which extended 

 for some distance beyond their ends, and adhered for its whole 

 length to the sides of the jar. 



Besides these little bodies, others, which I do not hesitate to 



