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I76NA TURE AND AFFINITIES OF THE SPONGES.whole cytoblastemic element in this species is remarkably tenacious orglutinous, and is drawn out in long strings, like bird-lime, when the spongeis broken apart the; granular cells observed by Barrois are evidently thespore-masses held together in the withdrawn glutinous threads of the investingcytoblastema. The so-called "sperm-balls," figured by F. E. Schulze,in relation with the genus Halisarca* would appear also to belong tothe same category. The abundantly distributed subspheroidal groups ofso-called coloured corpuscles figured and described bythis last-namedauthority as imparting the characteristic yellow tint to the keratose typeAplysina aerophoba, \ correspond remarkably with the yellow or lightbrown spores of Leucosolenia coriacea. Lastly, Metschnikoff's valuable" Spongologische Studien " J embraces abundant testimony in a correspondingdirection, and as is made evident at PI. X. Figs. 8 and 9 of thepresent treatise, reproducing his illustrations of the so-called " mesoderm "elements of the genus Siphonochatina.the adherentsIn anticipation of the argument that may be advanced byof the Metazoic interpretation of sponge structures, to the effect that thesporular bodies here figured and described, represent spermaticor malereproductive elements, it is only requisite to point still more emphaticallyto the fact that these spores distributed broadcast throughout the substanceof the cytoblastema may, as ascertained by the author, be met with andtraced onwards through every intermediate size and stage, from the singlespheroidal spore up to the adult collared monads or amoebiform cytoblasts ;the derivation of these spores through the splitting up into a granular orsporular mass of the entire substance of the matured collar-bearing zooidsbeing correspondingly substantiated. Their phenomena of production andcycle of development are, in fact, in all ways identical with those that obtainamong the typical Choano-Flagellata and ordinary Flagellata, and in allof which the spores derived by a similar segmentation of the parent bodydevelop first a simple monadiform or amoeboid phase, and after arriving atthe adult state revert once more to the amcebiform condition, becomequiescent, and are again resolved into minute spores. In the sponge, allthese transformations and developmental processes take place within thesubstance of the cytoblastema, which constitutes a suitable nidus for themessentially corresponding with the gelatinous matrix or zoocytium ofOphrydium, P halansterium, and Protospongia.While the evidence so far submitted suffices to indicate the closeconnection of the Spongida with the typical Infusoria - Flagellata, andalso explains, in connection with the phenomena last described, the mannerin which the general sponge-body is, by ever progressing internal sporeproduction,rapidly increased in size, certain other important featuresconnected with their reproduction remain to be recorded. Althoughthe scattering of the spores through, and their development within, the* 'Zeit. Wiss. Zool.,' Bd. xxviii., 1877. f Ibid., Bd. xxx., 1878.\ Ibid., Bd. xxxii., 1879.