Hyatt.] 68 [March 5, 



would build up tissue in place of loose aggregations of cells 

 and lead us on through a maze of lost or yet undiscovered spec- 

 ializations until we came to creatures like sponges, with perfect 

 male and female cells, but these not so fully localized in the 

 tissues as among the higher Metazoa, and the embryo and cells 

 of the membranes retaining many of the essential characteristics 

 and functions of the zoons in colonies of Protozoa. 



The distinctions between Metazoa and Protozoa had not been 

 announced by Haeckel and explained by Huxley (Journ. Linn. 

 Soc. 1876), when Clark wrote on the Infusoria. He was not 

 aware that the sponges belonged to the Metazoa, and very nat- 

 urally considered them as true Protozoons on account of the 

 collared and flagellated cells which he saw lining the interior of 

 Leucosolenia. How strong this evidence is may be seen by his 

 excellent drawings and observations, and by the fact that Carter, 

 the noted English authority on this branch, and Saville Kent, 

 also well known for his microscopical researches, both main- 

 tained the same opinion. The latter even still supports Clark's 

 views, asserting that the ciliated cells become encysted, and that 

 the sponge is not a Metazoon, but really a colonial form of Prot- 

 ozoa. 1 Investigators, however, with this exception, unite in 

 describing the reproductive bodies in the mesoderm of sponges 

 as having true segmentation and being ova. In fact any one who 

 has seen them clearly can hardly come to any other conclusion 

 independently of the fact that they have been followed through 

 their various stages to the sponge form in several species. 



We have not seen the impregnation of the egg, nor has 

 any one up to the present time. No bodies similar to polar 

 globules have been noticed, though the stages in which such. 

 bodies ought to have been seen were very often under observa- 

 tion. Keller who sought for them in Chalinula notes their 

 absence, and they were also not seen by Schultze in Sycandra, 

 or other authors in other types. We are, however, able to do 

 something towards filling gaj3S in the history of the develop- 

 ment of sponges by observations on the ova and larvae of several 

 species, collected and studied at Eastport, Maine, in 1876. These 

 observations were too incomplete, wdien made, to merit special 



1 Biitschli also has lately supported the same view. (Zool. Anzeig., 1884.) 



