310 



Proceedings of the Royal Physical Society. 



XXI. Preliminary Note on the Development of Cribrella 

 oculata. By Arthur T. Masterman, M.A., D.Sc, 

 Lecturer in Zoology at the Nevj School of Medicine, 

 EdinUirgh. [Plate IX.] 



(Read 21st March 1900.) 



Crihrella oculata and Asterias Mulleri are two common 

 star-fishes of our coasts which have demersal larvae enclosed 

 in a "brood- cavity" formed by the arms of the mother. 

 The stages of the former have been figured externally to 

 some extent by Sars many years ago. The development 

 itself has some very peculiar features, which should prove 

 full of interest to morphologists. The main points are 

 these : — 



1. The segmentation is at first total and unequal, closely 

 resembling that of the frog, but later a free cell-formation 

 occurs through the whole egg, and a solid morula is finally 

 produced, with cells of equal size throughout. 



