Prof. Allman on the Hydroid Zoojihytes, 53 



posterior part of the body of the polype in the form of a funnel- 

 shaped cup, which does not, however, extend as far as the origin 

 of the tentacles, and which, though it reminds us of the polype- 

 cell in the Campanularian zoophytes, is incapable of receiving 

 the tentacles and anterior part of the polype even in extreme 

 retraction. 



The tentacula are seated near the middle of the club-shaped 

 body. They are about ten in number, and are arranged in a 

 single verticil. Their cavity presents the septate appearance 

 usual in the marine polypes ; but under slight pressure the con- 

 tents of the stomach are easily forced into them without any 

 evident rupture of the tissues. 



The body in front of the tentacles is continued into a long, 

 conical, but mutable, mouth-bearing process. 



The gonophores are remarkably large, and are chiefly formed 

 upon the main stem and primary branches. They are of an 

 oval figure, each borne on a long peduncle which issues from 

 the summit of a very short lateral ramulus, invested like the other 

 branches with a proper polypary, which is here, exactly as in 

 the polypiferous ramuli, dilated at its summit so as to form a 

 conical cup, from whose centre the peduncle of the gonophore 

 springs. 



The contents of the gonophores in this species are sporosacs ; 

 and in the structure of these there are some points which deserve 

 attention. Lining the inner surface of the ectotheque, and in- 

 terposed between it and the endotheque or sac which imme- 

 diately confines the generative elements, is a third investment, 

 which is plainly homologous with the umbrella of a Medusa. 

 It supports upon its inner side four (or more ?) short radiating 

 canals, which spring from the base of the manubrium, and, after 

 running forwards for a short distance, terminate each in a blind 

 extremity. There is no trace of a circular canal. 



We have thus, in the present zoophyte, a form of sporosac 

 intermediate between that met with in Tubularia, with its well- 

 developed umbrella and radiating and circular canals, and that 

 which occurs in the greater number of cases where the umbrella 

 has entirely disappeared. 



When the gonophores approach maturity, they present upon 

 their summit a well-defined prominent opening destined to give 

 exit to the ova or spermatozoa. 



The ova possess a deep-orange vitellus, but otherwise pre- 

 sent nothing peculiar. They have a distinct germinal vesicle 

 and germinal spot, and, as in most of the Hydroid zoophytes, 

 become transformed into a Leucophrydiform embryo. 



The spermatogenous tissue of the male sporosac presents very 

 distinctly the appearance of radiating striae, indicating a com- 



