24 

 2. Linnean Society of London. 



18. Decbre. 1879. — Note on the Podocysts of the Hydroida. — Prof. 

 Allman drew attention to the fact of his having some years ago (Phil. 

 Trans. 1875) described the occurrence in Myriothela of certain remarkable 

 pedunculated sacs which are formed in the spherical capitulum of the ten- 

 tacles, where they are in connection with a bulbous mass composed of radia- 

 ting filaments. These filaments admit of a comparison with the rod-like 

 bodies characteristic of special sense organs in higher animals : and the whole 

 structure was believed by the author to represent in Myriothela an apparatus 

 of special sense. For these pedunculated sacs Prof. Allman proposes the 

 designation of »Podocysts« and he now believes that in more or less modified 

 forms they are more widely distributed among the Hydroida than he had 

 supposed when he described them in Myriothela. He would refer to the 

 same group of bodies the pedunculated thread-cell-like sacs which in the 

 form of four pencils terminate the four lobes which surround the mouth of 

 the planoblast in Podocoryne (see Gymnoblastic Hydroids, PI. XVI, figs. 6, 7). 

 Here, however, instead of being immersed in the surrounding tissues , they 

 stand out free from the surface and are bathed on all sides by the water. 

 Each sac is furnished with a minute terminal style, as in Myriothela. Whether 

 the very singular pedunculated sacs with which the tentacles are armed in the 

 planoblast of Gemmaria (Gymnoblastic Hydroids , PI. VIII, figs. 3, 4) must 

 be placed in the same general category with the »podocysts« of Myriothela is 

 not at present so evident. Instead of containing, as in the latter, a single 

 thread-cell-like body the sacs of Gemmaria enclose several oval capsules, whue 

 the terminal style of the »podocyst« of Myriothela is here replaced by a pencil 

 of long vibratile cilia. The peduncle of the sac moreover is in Gemmaria 

 eminently contractile, at one time extending itself to a great length and again 

 becoming so much shortened as to bring the sac which it carries on its sum- 

 mit almost in contact with the tentacle of the planoblast. Notwithstanding, 

 however, these difi'erences the correspondance is still so close as to suggest 

 a similar significance. — J. Murie. 



IV. Personal-Notizen. 



Frankfurt a. M. 



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