370 M. F. E. Schulze on the Relationship 



of when he succeeded in discovering and studying the deve- 

 lopment of a Choanoflagellate form which, in the fully deve- 

 loped state, constitutes an adherent colony, and secretes a 

 hyaline gelatinous substance in which all the individual 

 animals are imbedded, partly in their typical development, 

 and partly in various stages of development and metamor- 

 phosis. 



The transformation of the individuals furnished with a flagel- 

 lum and collar into irregular amoeboid cells, from eacli of 

 which a mass of spores is then developed by continued division, 

 is easier to observe in this than in any other Choanoflagellate. 

 But, according to Saville Kent's view, the spores pass through 

 a stage furnished only with a flagellum in their transformation 

 into the characteristic collared cells, which again, by division 

 and the secretion of gelatinous basal substance, give origin to 

 new colonies. Saville Kent names this newly-discovered 

 Choanoflagellate Protospongia Hceckelii, and repeatedly re- 

 fers to its great resemblance to the Sponges. To produce a 

 sponge, although a very simple one, all that is necessary, he 

 thinks, is a trifling modification in the position of the zooids, 

 which would merely have to retreat, in the fashion of nests, 

 into invaginations of the gelatinous " zoocytium.'" He fur- 

 ther indicates that, even histologically, there is no essential 

 difference between his Protospongia and a skeletonless sponge, 

 seeing that not only do the individual animals of the Choano- 

 flagellata resemble the collared cells of the Sponges, but even 

 the gelatinous substance which serves as the common imbed- 

 ding mass of the Protospo?igia-co\ony agrees with that mass 

 of tissue which acts as the basis and supporting framework 

 for the epithelial layer of the sponge-body. 



Now it is well known that this fundamental tissue of the 

 Sponges, in which alone the skeletal parts are developed, has 

 been interpreted in very different ways. Described by Oscar 

 Schmidt as sarcode and by Hackel as syncytium, it is under- 

 stood by both as if its hyaline basal substance, which contains 

 granules here and there, were produced by the fusion of the 

 protoplasmic bodies of neighbouring cells, and itself contrac- 

 tile. Of these cells only the nuclei are preserved. 



In opposition to this view I have demonstrated, in a series 

 of monographs upon certain families, genera, and species of 

 Sponges which I have been able to investigate in the living 

 state, that we have to do here not with such a syncytium, 

 but with a true connective substance. I have shown that 

 in the tissue in question well-individualized, more or less 

 distinctly limited cells with nucleus and plasma-body are to 

 be recognized, and that these lie in a basal substance, which is 



