I 76 NA TURE AND AFFINITIES OF THE SPONGES. 





 whole cytoblastemic element in this species is remarkably tenacious or 



glutinous, and is drawn out in long strings, like bird-lime, when the sponge 

 is broken apart ; the granular cells observed by Barrois are evidently the 

 spore-masses held together in the withdrawn glutinous threads of the invest- 

 ing cytoblastema. The so-called "sperm-balls," figured by F. E. Schulze, 

 in relation with the genus Halisarca* would appear also to belong to 

 the same category. The abundantly distributed subspheroidal groups of 

 so-called coloured corpuscles figured and described by this last-named 

 authority as imparting the characteristic yellow tint to the keratose type 

 Aplysina aerophoba, \ correspond remarkably with the yellow or light 

 brown spores of Leucosolenia coriacea. Lastly, Metschnikoff's valuable 

 " Spongologische Studien " J embraces abundant testimony in a corre- 

 sponding direction, and as is made evident at PI. X. Figs. 8 and 9 of the 

 present treatise, reproducing his illustrations of the so-called " mesoderm " 

 elements of the genus Siphonochatina. 



In anticipation of the argument that may be advanced by the adherents 

 of the Metazoic interpretation of sponge structures, to the effect that the 

 sporular bodies here figured and described, represent spermatic or male 

 reproductive elements, it is only requisite to point still more emphatically 

 to the fact that these spores distributed broadcast throughout the substance 

 of the cytoblastema may, as ascertained by the author, be met with and 

 traced onwards through every intermediate size and stage, from the single 

 spheroidal spore up to the adult collared monads or amoebiform cytoblasts ; 

 the derivation of these spores through the splitting up into a granular or 

 sporular mass of the entire substance of the matured collar-bearing zooids 

 being correspondingly substantiated. Their phenomena of production and 

 cycle of development are, in fact, in all ways identical with those that obtain 

 among the typical Choano-Flagellata and ordinary Flagellata, and in all 

 of which the spores derived by a similar segmentation of the parent body 

 develop first a simple monadiform or amoeboid phase, and after arriving at 

 the adult state revert once more to the amcebiform condition, become 

 quiescent, and are again resolved into minute spores. In the sponge, all 

 these transformations and developmental processes take place within the 

 substance of the cytoblastema, which constitutes a suitable nidus for them 

 essentially corresponding with the gelatinous matrix or zoocytium of 

 Ophrydium, P halansterium, and Protospongia. 



While the evidence so far submitted suffices to indicate the close 

 connection of the Spongida with the typical Infusoria - Flagellata, and 

 also explains, in connection with the phenomena last described, the manner 

 in which the general sponge-body is, by ever progressing internal spore- 

 production, rapidly increased in size, certain other important features 

 connected with their reproduction remain to be recorded. Although 

 the 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. 



