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Show 138 MR. G. H. FOWLER ON A N E W PENNATULA. [Feb. 21, The appearances seen in a transverse section of the immature autozooids are of some interest, and bear out the cone usions of Hickson (loc. cit.) and of Wilson (" Development of Renilla, mil. Trans, vol. 174, p. 723). These immature polyps are not as yet provided with tentacles, but possess stomatodeea and the usual eight mesenteries. Of these latter, the two axial (dorsal) mesenteries, in the youngest autozooids, as in the mature siphonozoords, alone exhibit mesenterial filaments of the characteristic bilobate shape; the cells of which tbe lobes are constituted contain deeply staining nuclei, and histologically agree with the ectoderm of the stomato-dseum from which they are derived. As was shown by Hickson, no siphonoglyphe is recognizable in the mature autozooids of Pennatula; but in the youngest autozooids, which are much compressed at right angles to the usual direction (i.e., in an axial-abaxial plane), I find that the whole of the abaxial side of the stomatodaeum is clothed by very long columnar cells, with numerous deeply staining nuclei, and bearing long stout cilia, these appearances being entirely characteristic of a siphonoglyphe ; this region is marked off from the remaining three fifths of the stomatodseum by a ridge on either side, and constitutes indisputably a true siphonoglyphe. The somewhat older autozooids, which are nevertheless hardly mature, exhibit filaments on the lower six, as well as on the axial two, mesenteries ; these filaments are of endodermic origin, and consist merely of an aggregation of pyriform cells, resembling those figured by Wilson (/. c. pi. Ix. figs. 145, 146), but more swollen. Proportionately to their age and development, the siphonoglyphe of the autozooids becomes less and less marked, till in the fully mature polyps no trace of it is to he recognized. This occurrence of a siphonoglyphe in the ontogeny of the autozooids is a point of some considerable interest. Knowing so little as we do of the stimulus that causes a developing ovum to recapitulate its ancestral history, we should hardly be justified in asserting that such recapitulation might not also occur in asexual reproduction. The colonial ancestor of the Octactinise (Alcyonaria) resembled the existing Alcyonium in the absence of dimorphism and the possession of a siphonoglyphe ; morphological differentiation, correlated with division of labour, resulted, among such descendants as the Pennatulida, in the production of autozooids (nutritive and sexual polyps, devoid of a siphonoglyphe) arrd of siphonozooids (circulatory or respiratory polyps, incapable of generation and of nutrition, but provided with a strong siphonoghphe in order to effect the circulation of "chylaqueous fluid" through the colony). If then, as appeals to me to be the case, the very considerable size aud number of the siphonozooids contrasted with the paucity of the immature autozooids, together with the loss of the siphonoglyphe as maturity is attained, point to the functional uselessness of this organ in the young buds, we are driven to the conclusion that we have here to deal with a case in which asexual ontogeny is repeating phylogeny. As was described by Wilson (Mitth. Zool. Sta. Neapel, v.) in the buds of Renilla, the two axial mesenterial filaments appear before |