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PROCEEDINGS OP THE 



[April, 1857. 



Medusa-bearing capsules have been observed from April to 

 October, and probably the production of medusae only ceases in 

 the dead of winter, between December and February. 



2nd group SERTULARID^E. 



The Larvae have their polyps protected by a cell-like expansion 

 of the horny covering of the polypidom as among Campanularidae, 

 but their cells are sessile upon the main stem or its branches. 

 The polyps themselves want the proboscidiform mouth which 

 characterizes the last group. There are no known instances in 

 which the Medusae become free. They are developed in large 

 capsules as in Campanularidae, but remain mere cysts enveloping 

 the sexual products. 



In this group there is a particular tendency manifest to a group- 

 ing of the individual polyps in such a manner as to subordinate their 

 individuality to the idea of the group. Thus we frequently find 

 that the individual polyp-cells in a given section of the stem are 

 unlike each other, and that the tenant of one only of them attains 

 the fully developed polyp-form, while the remainder undeveloped 

 are grouped round it in various patterns according to the genus. 

 This grouping also is frequently visible in the prolific vesicles, 

 producing what may be called compound vesicles. Instances of 

 these peculiarities, such as Aglaophenia and Plumularia, will be 

 noticed further on. 



We should not overlook in this connection the possibility that 

 the presence or absence of this compound character may be the 

 means of distinguishing two minor groups among Sertularidae. 

 Sertularia, Thuiaria and Dinarnena, as apparently also some 

 plume-like species hitherto included in Plumularia, have no lesser 

 polyps, while Antennularia, Plumularia, (which probably contains 

 the types of several genera,) and Aglaophenia, {vide infra) all have 

 lesser as well as great polyps, and their genera may be distin- 

 guished by the manner in which these are grouped together. Of 

 these two groups Plumularidae would, on the whole, from the gen- 

 erally funnel-shape of the polyp-cells, make a nearer approach to 

 Campanularidae than would Sertularidae proper, whose cells are 

 usually more tubular or even of less diameter at the aperture than 

 below it. I have, however, refrained from insisting upon thus 

 subdividing the group on account of my ignorance of the Euro- 

 pean species, the descriptions and figures of which by European 

 authors, appear to leave much to be desired. 



