1884.] 101 [Hyatt. 



to consider these apparent buds as really localized extensions of 

 the primitive central ciliated chamber of the ascon. The ampullae 

 being derived from extensions of the smooth epithelium of the 

 young cannot be estimated as primitive organs or as the equiva- 

 lents of the gastrula. They are branches, diverticula, or organs, but 

 not equivalent individuals, persons or zoons. Haeckel's view (Cal- 

 cisp. p. 116-188), if we understand his comparisons, differs essen- 

 tially. According to his theory a sycon is formed by strobiloid 

 gemmation, and each radial tube is the equivalent of a " person " or 

 an ascon, though he apparently takes the view that the ampullae 

 are organs. To this illustrious auther true antimera do not exist 

 in the sponges, whereas we find indistinct and primitive antimera 

 in the ampullae. We cannot agree also with the result of his 

 comparisons that the sycon and other compound sponges are to 

 be defined as having the buds of the primitive colonial forms 

 united so as to form an individual. This result and Haeckel's 

 opinion, that the intermediate canals which are found in some 

 sponges are due to the imperfect junction of strobiloid buds in 

 the building up of compound forms, have been dissented from by 

 Vosmaer. This author asserts (Bronn's Thierreichs, vol. n, Porif- 

 era, p. 136), that in no case does the surface of a Sycon grow out 

 into buds, but that the tubes are bound together because they 

 grow in the mass of the tissue. Vosmaer also describes the 

 " intercanal system " as consisting of true lacunae which open as 

 the mesoderm thickens, and cannot be considered as tubes left open 

 by the imperfect junction of individuals, or the walls of the col- 

 ony as in any sense due to infoldings of the ectoderm of the sponge. 

 The gastrula, according to Haeckel, indicates, that a " person " 

 is any sponge or branch of a massive sponge, which has but one 

 cloacal aperture, whereas in our view the opening of the gastrula 

 is not the homologue of the cloacal tube nor of a stomodeum. 

 Any number of stomodea may exist in a sponge or any part 

 of one, since they are merely primitive invaginations of the 

 ectoderm without distinct localization in the adults, and subject 

 to variation even in the young, though with a tendency in many 

 forms to appear at the pole opposite the blastopore, and arising 

 in the primitive osculum, or outlet of the gastro-vascular 

 system. 



If, as we suppose, the ampullae are antimera, homologous 



