REPRODUCTION IN GRANTIA COMPRESSA. 



By OLGA M. JORGENSEN. 



The following observations on the common calcareous sponge 

 of our coast, Grantia compressa, were made from serial sections 

 of material collected at CuUercoats at short intervals between 

 July, 1915, and July, 1916, fixed in formalcohol, decalcified and 

 stained in iron hsemotoxylin. The specimens fixed varied from 

 \ to I inch m length, and were sectioned both longitudinally and 

 transversely. 



Breeding Season. — My intention was to determine the time 

 at which the germ cells appeared and were developed in this sponge 

 by taking successive batches of material, but the first specimens 

 obtamed, from July 22nd to 27th, showed large quantities of fully 

 developed ova, together ^\ith numerous well grown embryos, so 

 that the earhest stages were lost. 



A Httle later, August 17th, the sections showed a great 

 decrease in the number of ova though older stages of embryos 

 were still plentiful. On September 4th, no embryos remained 

 within the maternal tissues. 



Further collections were made every few weeks, but no repro- 

 ductive bodies were observed until June, 1916, when very small 

 germ cells made their appearance. Thus it would appear that 

 on the Northumberland coast the breeding season of G. compressa 

 lasts from June to the beginning of September. This is strikingly 

 different from what takes place m the species at Plymouth, as 

 shown by Mr. Orton's work there (1). He states that G. com- 

 pressa is an annual s^Donge, growing and breeding in spring and 

 summer and disintegrating m autumn. Breeding begins in April, 

 the embryos being freed in June. The fact that embryonic stages 

 are still plentiful in August indicates the occurrence of two breeding 

 seasons — the larger {i.e., the older) specimens reproduce early, 

 giving rise to larvae which grow rapidly and are themselves able 



