The porifera and coelentera . t believes them to be then completely absorbed, the whole spongedeveloping, as Gutte supposed, from the inner mass alone. The careful investigations, recently published, of Evans [34] showthat, as might be expected from a comparative survey of sponge embryology,the Hagellated cells of the larva do furnish the collar cells of the adult, butthat they may be supplemented in this function by other cells of the larvain a very interesting manner. In the inner mass there are always to befound large granular cells, similar both in appearance and potentialities toblastomer
The porifera and coelentera . t believes them to be then completely absorbed, the whole spongedeveloping, as Gutte supposed, from the inner mass alone. The careful investigations, recently published, of Evans [34] showthat, as might be expected from a comparative survey of sponge embryology,the Hagellated cells of the larva do furnish the collar cells of the adult, butthat they may be supplemented in this function by other cells of the larvain a very interesting manner. In the inner mass there are always to befound large granular cells, similar both in appearance and potentialities toblastomeres of the segmenting ovum or to cells of the gemmule, and markedout by containing a large amount of reserve food material (nutritivevacuoles and yolk-granules). These cells are to be regarded as archaeocytes,which are able to give rise to tissue cells of any kind ; while, on the onehand, their destiny, so long as they remain unmodified, is probably to be-come the amoebocytes of the adult, they may, on the other hand, in their. Five stages in the developinent of a Hagellated chamber from a blastomere in the inner inassof Spongilld. 1, a blastomere and two cells of the inner mass ; 2, the nnclear corpnscle of theblastomere has broken up into a number of chromatin bodies within the nnclear membrane ; 3,the nucleus of the blastomere has become fragmented ; 4, the small nuclei so produced havearranged themselves at the periphery of the cell, the cytoplasm of which is beginning to showlines (if cleavave between them ; 5, the original blastomere has broken up into a number ofcollar cells, arranged in a chamber ; the two cells of the inner mass form part of the epitheliumof the excurrent canal. Slightly schematised. (After Evans.) capacity of reproductive cells (tokocytes) contribute towards either thedermal or the gastral layer. In the latter case they undergo a sort offragmentation, affecting first the nucleus and then the cytoplasm, andresulting in the formation of a number of small
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