12 HYDROIDA 



of the tentacles is simple, with no central cavity, and with a thin snpporting lamella without any 

 particular thickening. In the endoderm we must distinguish between an oral portion, abounding 

 in mucous gland cells, and the gastral portion proper. The colonies develop no calcareous skeleton". 



It is questionable, as is also pointed out by Kiihn (1913), whether it is justifiable to maintain 

 the Corynidae and the Pcnnariidac as two distinct families. Stechow (1913) states that "das gleich- 

 zeitige Vorkommen geknopfter und fadenformiger Tentakel ein vorziigliches Merknial fiir das Bestira- 

 men ist"; simultaneously, however, he ranks the genera Acaulis and Clavaiclla with the Corynidae^ 

 though, having tentacles both capitate and filiform, they should, from this main characteristic, be 

 reckoned among the Pcimanidae. Also as compared with the Ttilnilariidae, the limitation of the Pcnnarii- 

 dae makes some difficulty. Thus Bonne vie (1899) e. g. classes Hcterostephamis among the Tu- 

 bulariidac in spite of the fact that the species is provided with capitate distal tentacles. Stechow 

 (1913), on the other hand, as well as Broch (1911), ranks this genus with the Pcnnariidac. I regret 

 that I am in lack of material for a more thorough inquiry into the Pcnnariidac ; it is not unlikely 

 that the anatomical structure of the polypes might afford safer holds for the judging of this group of 

 hydroids than the merely outward morphological characters. 



The Corynidae form a very central groiip, with which all the other groups of the section of 

 Capilata., stated by Kiihn, are likely to have originated. — At the first glance it may appear as if 

 one of the genera Alonocorync has got uematocysts heterogeneously developed, so as to show, be- 

 sides oviform or globular capsules, partly also long, narrowly oval ones. That this is not the case, is ascer- 

 tained by a careful study of material of Monocoryne gigantea (Bonne vie) collected in the 

 Trondhjemsfjord. Partly all the uematocysts of this shape are discharged, and partly developmental 

 stages of other uematocysts than oviform ones are not traceable. It is, therefore, obvious that, in 

 l^eiug discharged, the oviform uematocysts assume a narrowly oval shape. The apparent dimorphism 

 of the nematocysts would otherwise have been greatly interesting as a connecting link with Myrio- 

 f/icla, and would have been likely to sujjport the supposition of Bonne vie (1899) of the derivation of 

 the last-mentioned genus from the Corynidae through Monocoryne. But as a matter of fact, the large 

 Monocoryne gigantea shows the anatomical structure of the true Corynidae. Swenander (1903) mentions 

 that its tentacles are coalesced at the basis; this statement, however, only holds good for the ectoderm, 

 which in several places appears to be stratified; the endoderm, as far as the single tentacles are con- 

 cerned, continues, wholly surrounded by the ectoderm, to the supporting lamella. Monocoryne gigantea 

 presents another peculiarity which llu- inciuircrs have hitherto obviously failed to notice; the indivi- 

 duals are hermaphrodite, in a most peculiar way. Not only we find in a single individual sheer female 

 and sheer male gonophores; but among these also occur several gonophores containing, besides large 

 ova, also sperms and spermatocytes of all stages. The gonophores of this species are reduced to 

 cryptomedusoids. 



In the internal structure of the polype of the Corynidae our attention is fixed on a great ac- 

 cumulation of mucous gland cells in the endoderm next to the orifice. Here are densely accumulated 

 a lot of cells, whose affinity with Delafield's haematoxyline make them very conspicuous on material 

 well preserved. This concentrated glandular zone is found still more strongly marked in the Myrio- 



