118 



THE MICROSCOPE AND ITS REVELATIONS. 



issuing. The in-current brings into the chambers both food-material 

 and oxygen; and from the manner in which colored particles experiment- 

 ally diffused through the water wherein a Sponge is living, are received 

 into its sarcodic substance, it seems clear that the nutrition of the entire 

 fabric is the resultant of the feeding action of the separate amoeboid and 

 flagellate units, each of which takes-in, after its kind, the food-particles 

 brought by the current of water, and imparts the product of its digestion 

 of them to the general sarcodic mass. 1 



509. The continuous sarcode-substance or ' cyloblastema ' that clothes 

 the skeleton of the Sponge and constitutes its living body, includes great 

 numbers of 'cytodes ( 392), in various stages of development; which, 

 like isolated Amwbce, are constantly undergoing changes in form and 

 position. Their long slender pseudopodia, radiating towards those of 

 their neighbors, often unite together to form a complex network; and it 

 seems to be by their agency, that the continual contractions and expan- 

 sions of the oscula are produced, which are very characteristic of the 

 living Sponge. It would seem, indeed, as if they combined in them- 

 selves the functions of nerve and muscle-elements, which are differenti- 

 ated in the higher forms of 



FIG. 351. animal life. Any one of 



these amoeboids, again, de- 

 tached from the mass, may 

 lay the foundation of a new 

 ' colony.' In the aggregate 

 mass produced by its con- 

 tinuous segmentation, cer- 

 tain globular clusters are 

 distinguishable, each hav- 

 ing a cavity in its interior; 

 and the amoeboids that form 

 the wall of this cavity be- 

 come metamorpliosed into 

 collared flagellate zooids 



Diagrammatic section of Spongilla: a, a, superficial 

 layer; 6, inhalant apertures; c, c, flagellated chambers; d, 



exhalant oscule; e, deeper substance of the sponge. 



whose flagella project into it. 

 Thus is formed one of the characteristic ' ampullaceous sacs;' which, at 

 first closed, afterwards communicates with the exterior, on the one hand, 

 by an incurrent passage, and on the other with the excurrent canal-system 

 leading to the oscula. Besides this reproduction by ' micro-spores/ 

 there is another form of non-sexual reproduction by ( macro-spores ;' 

 which are clusters of amoeboids encysted in firm capsules, frequently 

 strengthened on their exterior by a layer of spicules of very peculiar 

 form. These ' seed-like bodies,' which answer to the encysted states of 

 many protophytes, are met with in the substance of the sponge, chiefly 

 in winter; and after being set free through the oscula, they give exit to 

 their contained amoeboids, each of which may found a new colony. A 



1 This view of the nature and living action of Sponges, originally suggested by 

 Dujardin, was definitely put forth by the late Prof. H. James-Clark, as the result 

 of an admirable series of researches on Sponges and Flagellate Infusoria, in the 

 Transactions of the Boston Society of Natural History for 1868, reproduced in the 

 "Ann. Nat. Hist." for the same year. See also his Memoir on Spongilla in 

 " Amer. Journ. Sci.," 1871, pp. 426-436; reproduced in * Monthly Microsc. Journ.," 

 Vol. vii., (1872), p. 104. His observations have been since fully confirmed by 

 Messrs. Carter and Saville Kent; who have published a succession of Papers in 

 the " Annals of Natural History," the general conclusions of which are embodied 

 in Chap. v. of Mr. S. Kent's " Manual of the Infusoria." 



