SPONGES. 61 



the Metazoa, sj)ringing from the Protozoa, would show similar tendencies toward dif- 

 ferentiation of the colonies. If, as in the sponges, the lower forms had male and 

 female cells in the same body, then the progress of differentiation should lead to a 

 more decided separation of these functions so that some would produce only female 

 and others orjy male cells. In other words, the complete separation of the sexes would 

 take place by a perfectly natural transition, and we should have male metazoons and 

 female metazoons. 



The sponges are frequently regarded as degraded Metozoa, but to the author this 

 view seems highly improbable. Huxley first recognized the systematic importance of 

 the sponges, but contrasted them as a division with the rest of the Metazoa, while 

 MacAUlster, and subsequently the author, gave them their true taxonouiic rank as an 

 independent branch of the animal kingdom. 



Class I. — CALCISPONGI^. 



This division is somewhat inappropriately named for the reason that some of the 

 genera have no skeletons, but this objection might, with equal justice, be made with 

 regard to the names applied to the other groups. The animals of this class have fusi- 

 form or cylindrical bodies which may be single with one cloacal aperture, or branching 

 with an aperture at the end of each branch, or more or less solid as in the other 

 sponges. When a skeleton is present, the spicules which comj)Ose it consist of carbo- 

 nate of lime, and their longer axes are arranged in lines parallel with the canals, that 

 is at right angles to the inner and outer walls of the sjjonge. 



Order I. — PHYSEMARIA. 



This order contains the remarkable genera, Haliphysema and Gastrophysema, 

 which, according to Haeckel, are nearer in form and structure to his archetypal animal 

 form, the gastrula, than are any other adult animals. They are small and vase-shaped 

 in Haliphysema, while Gastrophysema may have from two to five chambers. There is 

 but one aperture above, and the water is drawn into this by ciliary action. According 

 to Haeckel, the body wall consists of but two layers, the ectoderm and the endoderm, 

 but it is evident that the ectoderm of the German savant can be nothing else than 

 mesoderm, for it is composed of loose cells and intercellular protoplasm, while the true 

 ectoderm of all sponges is a simple pavement epithelium and never a compound tissue. 

 In Haeckel's figure, the whole interior of Halisphysema is paved with ciliated cells, 

 among which are interspersed amoeboid cells. Both Haeckel and Bowerbank deny the 

 existence of jjores, and it is not likely that even transitory openings would have 

 escajjed their observation. 



The strangest part of the history of the Physemaria is that both Carter and Saville- 

 Kent claim that Haliphysema is a true protozoon, and Kent's figure, which is as 

 specific as Haeckel's, depicts a true foraminifer. These observations render it very un- 

 certain whether the group should be referred to the sponges or to the Protozoa. 

 Gastrophysema may be a true sponge, and we therefore describe the order in this 

 connection. Mr. J. A. Ryder describes as an American representative of the group, a 

 curious club-shaped animal with a tough cortex and a cellular interior, under the name 

 Camaraphysema. 



