284 



MESSRS. C. SHEARER, W. DE MORGAN, AND H. M. FUCHS 



58 days. 50 well-developed larvae remained, some of which were commencing to 

 metamorphose. • 



(4) E. esculentus ^ X E. acutus $ . {Of. Plate 20, figs. 26-35.) 



Ou the whole this culture advanced rapidly. This may have been correlated with 

 a good growth of food, but was probably due in part to the ripeness of the sex cells. 



65 hours. Blastulae. No pigmentation. 



Gastrulae with very slight pigmentation. 



Prism larvae with rather heavy pigmentation. Commencement of antero- 

 lateral and postoral arms. 



Postero -dorsal arms advancing. Commencement of preoral arms. 



Apical rods spinous. 



8 -armed plutei. 



Anterior ciliated epaulettes in process of formation. 



Appearance of ^cAinws- rudiment. 



Posterior ciliated epaulettes present. Apical pedicellaria. Many at this 

 stage had also lateral pedicellariae. 



Large Ecliinus-x\i6\.VLi&n%. Posterior ciliated epaulettes closing round the 

 apical end. Two lateral and two posterior pedicellariae. 



Eventually nine metamorphosed. 



39 



65 hours. 



4 days. 



5 „ 



10 

 14 

 17 

 20 



26 



40 

 50 



70 



(5) E. acutus % X E. esculentus $ . {Cf. Plate 20, figs. 36-43.) 



Prism larvae, with a considerable amount of pigment. 



Arms appeared. Larvae well pigmented. 



A number of the larvae were seen to have irregular skeletons with lattice 



work and double rods in the postoral arms. 

 Postero-dorsal arms began to grow out, and the skeleton of the preoral 



arms appeared. 

 The apical rods very spinous. 



Little advance. Increase of pigmentation of the stippled acutus type. 

 Preoral lobes appeared, 

 ^"c/tm MS-rudimeut appeared and the anterior ciliated epaulettes 



commenced to thicken. 

 The Echinus-rudiment in the example figured was ou the right side, a 

 condition occasionally found. The anterior and posterior ciliated 

 epaulettes were well advanced. 

 Two pedicellariae, one posterior and one lateral. 

 Echinus -rudiment increased in size. Arms commencing to be reti'acted. 



Most had three pedicellariae, one posterior and two lateral. 

 A nimiber were about to metamorphose and were preserved. 



