DEVELOPMENT OF HALISARCA LOBULABIS. 60^ 



On the Development of Halisarca lobularis 

 (O. Schmidt). 



\V. J. Sollas, iff. 4., D.Sc, 



Late Fellow of Si. Jolni's College, Cambridge, Professor of Geology iu the 

 University of Dublin. 



With Plate XXXVII. 



In the summer of 1883, 1 spent— thanks to the hospitality 

 which Professor Lacaze Duthiers so generously extends towards 

 foreigners — some weeks in the Zoological Laboratory at Roscolf, 

 Brittany, and while there was permitted to preserve for sub- 

 sequent examination specimens which were not among the 

 immediate objects of my research at that time. In this way I 

 obtained several examples of both species of Halisarca, of 

 which on my return to England I cut numerous sections, and 

 then found that the specimens of Halisarca lobularis were 

 richly crowded with broods of embryos in various stages of 

 development. 



These specimens were collected from several localities in the 

 vicinity of Roscoff, some from the adjacent rocks of the beach, 

 and others from Douon, a rocky island composed of Archaean 

 schists, lying about four miles north-east of RoscoflF. At one 

 part of this island is a wonderful grotto, only accessible at low 

 water spring tides ; although open at both ends it affords suffi- 

 cient shelter from the powerful currents of the surrounding 

 sea to a tliick growth of many and brilliantly coloured animals, 

 which tapestry its walls, concealing them from sight. Be- 

 sides Ascidians and Anemones, there are numerous sponges, 



