The porifera and coelentera . nited by concrescence, givinrise to a continuous meuibiane, perforated for the passage of the Hagella(cf. Fig. 54). Recent researches have failed to conlirni these statements(cf, Vosmaer, Pekelharing, and Bidder), and the appearances seen by Sollasare attributed to defective preservation. The matter cannot yet be con-sidered as settled satisfactorily.^ Before leaving the subject of the collar cells, it is necessary to mentionthe frequently alleged transformation of collar cells and their subsequentimmigration into the parenchyma to recruit the ranks of other class
The porifera and coelentera . nited by concrescence, givinrise to a continuous meuibiane, perforated for the passage of the Hagella(cf. Fig. 54). Recent researches have failed to conlirni these statements(cf, Vosmaer, Pekelharing, and Bidder), and the appearances seen by Sollasare attributed to defective preservation. The matter cannot yet be con-sidered as settled satisfactorily.^ Before leaving the subject of the collar cells, it is necessary to mentionthe frequently alleged transformation of collar cells and their subsequentimmigration into the parenchyma to recruit the ranks of other classes ofcells. Bidder (1891) formerly asserted the origin of porocytes in Asconsfrom modification of collar cells, but this view is now hardly tenable inview of the recent investigations which put the origin of the porocytesfrom the dermal epithelium beyond a doubt (cf Minchin [17]). Morerecently Masterman (1894) has asserted that collar cells when full fedbecome amoeboid and pass into the parenchyma as trophocytes (see below, I. Flo. 54. Choanocytes with coalesced collars (Sollass membrane), after Sollas. A, longitudinalsection through two flagellated chambers of Anthastra ccrmrMtnis, Soli. ; B, diagram of thefenestrated membrane produced by coalescence of the collars, i, prosojiyles ; e, aphodi; e, ex-current canal; in, Sollass membrane. p. 58), and that further, after having distributed their nutriment to theparenchymal cells, they take up waste products and migrate to the surfaceof the body, where they act as nephrocytes. It seems more than probablethat statements are founded on mistaken observations. (5) TJie Archaeocytes represent in many the most importantcell layer of the sponge, but at the .same time the one which, up tothe present, has been least studied. They are in their nature un-specialised cells, scarcely modified in structure from the blastomeresof the ovum, and capable of giving rise again, as cells, to thewhole organism or, in the gemmules, t
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