NOTES ON THE DEVELOPMENT OF SOME 

 SPONGES. 1 



HENRY V. WILSON. 



The following notes deal with the gemmule development of 

 Esperella jibrexilis (n. sp.) and Tedania Brucei (n. sp.), to which 

 are added a few observations on the egg development of Teda- 

 nione fcetida (n.g.) and Hircinia acuta. Esperella fibrex. is a 

 small silicious sponge abundant near Wood's Holl, Mass. The 

 others are Bahama forms found at Green Turtle Cay, the two 

 silicious sponges, Tedania and Tedanione being closely related. 



During the summer, Esperella and Tedania contain great 

 numbers of good-sized embryos in all stages of development, and 

 if the sponges are kept in aquaria for a few hours, some of the 

 embryos will pass out through the oscula. The embryos thus 

 set free are solid oval bodies covered with cilia, and are quite 

 like the egg larvae of many silicious sponges. They swim about 

 for a day or so and then attach themselves to the wall of the 

 dish, flatten out and undergo a metamorphosis. When the 

 embryos inside the mother are examined, they are found not to 

 be egg embryos, but true gemmules, i.e. internal buds. 



I will first describe the development of Esperella. The 

 mesoderm of Esperella contains cells which differ greatly in size 

 and general appearance, though they shade one into the other, 

 Some of the cells are much larger than the rest and have plump 

 bodies which stain well. Such cells congregate together and 

 form irregular groups in which the cells are rather closely 

 packed. The group of cells rounds itself off, the outer cells 

 becoming flattened and forming a follicle. The gemmule, as 

 thus formed, is at first quite small, often showing not more than 

 five cells in section, though a considerably larger gemmule may 

 be directly formed from a group of cells (Fig. i). The cells of 

 the gemmule, once the follicle is formed, are very closely packed. 



1 Published by permission of Hon. Marshall McDonald, U. S. Commissioner of 

 Fish and Fisheries. 



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