CAMPANULAEID^l. 99 



but this only becomes distinctly recognizable at a more advanced stage 

 of growth. 



(241.) The trunk continues to rise vertically upwards, and ulti- 

 mately produces at its summit a solitary cell, in which a " male " 

 (nutritive) polyp is gradually developed ; and then, as growth ad- 

 vances, secondary ramifications are developed, after the pattern peculiar 

 to the species. 



(242.) Another important fact in connexion with the history of the 

 Hydrozoa is, that in the compound species there exist male branches 

 as well as female branches upon the same polypary, the latter pro- 

 ducing ovigerous vesicles, whilst in the former the ova are replaced by 

 seminal capsules; these almost precisely resemble the "female cap- 

 sules " (Beroeform, c/emmce) figured by Loven, and are, in like manner, 

 surmounted by a circle of tentacula. 



(243.) CAMPANTTLARIDJE. The polypary or common integument of 

 these zoophytes is composed of a semigelatinous horny substance (fig. 47). 

 The older stems assume a dark-brown colour and a consistence resem- 

 bling that of horn. The young branches, on the contrary, and more 

 particularly the polyp-cells, are thin and perfectly diaphanous. The 

 polypary always exhibits a principal trunk, from which the different 

 branches proceed, every one of the latter being terminated by -a bell- 

 shaped cell. 



(244.) In the earlier stages of growth the polypary consists of a pri- 

 mary trunk, from which alternating pedicles are given off at regular 

 distances. These pedicles soon become transformed into branches, on 

 which new pedicles in turn make their appearance, as they did on the 

 original stem, exhibiting a dichotomous or trichotomous arrangement. 



(245.) At the base of each branch transverse rings are formed 

 (fig. 47, g}, which are persistent during the life of the polypary. All 

 the branches, as well as the common trunk, increase in their dimensions 

 in accordance with the age of the zoophyte ; and, as in vegetables, there 

 is a relation preserved between the thickness of the trunk and the 

 number and extent of the branches. 



(246.) Each polyp-bearing cell at the extremities of the branches 

 presents externally a bell-shaped cup, having at its bottom a horny dia- 

 phragm, perforated in the centre. It is through this perforation that the 

 body of the polyp is brought into communication with the common 

 fleshy substance of the polypary, and through its intermedium, with the 

 other polyps. 



(247.) From the recent observations of Van Beneden* relative to 

 the embryogeny of the Campanularian polyps, it would appear that they 

 frequently undergo, during their development, a series of changes not 

 less wonderful than those exhibited by the other Hydriform races whose 

 history has been carefully traced. 



* Nouveaux Mem. de 1'Acad. de Bruxelles, vol. xvii. (1843). 



H2 



