BY DR. R. VON LENDENFELD. 151 



been overlooked by other observers," which are exactly like the 

 monads, the spongozoa, which compose the adult sponge. The 

 cells lose their fringes and cilia, and coalesce into a Syncytium, 

 and the sponge soon forms. The embryo does not pass a Blastula 

 stage. Every one of the embryonic cells lives independently as a 

 separate animal through all these stages. The "so called ovum, 

 with amoeboid movement, which, according to Haeckel and 

 others, is the independent product of the imaginary entodercn," is 

 an ordinary Spongozoan which has lost its fringe. In a similar 

 way, as the " gemmules" also, the cilated chambers are formed. 



Barrois (157) made some interesting observations on the 

 embryology of different sponges. In most cases the embryo 

 remains solid throughout, and the canal system is formed after, 

 wards in the Mesoderm. He describes the formation of the 

 Morula very accurately. His observations tend to prove the 

 correctness of the previous statements of F. E. Schulze. 



Schultze (158) describes the embryology of a great many 

 different sponges. The ovum is fructified within the sponge and 

 divides. No Morula is formed in the calcareous sponges, the stage 

 with sixteen cells is already a Blastula. The Blastula consists of 

 cylindrical small transpai-ent, and rounded intransparent cells ; 

 the whole having the shape of an acorn, the intransparent cells 

 forming the cup. 



The transparent cells — evidently the Ectodermal elements — are 

 invaginated. The morphological Ectoderm of the so formed 

 Gastrula is physiologically an Entoderm. 



The Larva swims about and finallv affixes itself by means of 

 pseudopodial processes given off from the Ectodermal cells. 



By a complicated folding process the original sac is converted 

 into a large mass traversed by two systems of canals, one being 

 ectodermal and the other entodermal. (Calcispongiae.) In other 

 sponges the process is different. 



(157). C. Barrois. Embriology des quelques Eponges de la manche. 

 Annales des sciences Naturelles. Zool. VI. ser. Ill , Art. 9. 

 (158). F. E. Schultze (I.e.). 



