1887.] On the early Development of Antedon rosacea. 



2\)1 



Considerable light is thrown upon the phenomena of cohesion and 

 adhesion by this method of investigation ; and especially on the Un- 

 differentiated state of organs when in congenital union. This, if 

 thoroughly understood, completely clears up the difficulties surround- 

 ing the interpretation of the " receptacular tube" and the "inferior 

 ovary." 



The investigation into the character and distribution of the 

 vascular cords reveals the true nature of the axile and free central 

 placentations ; in the former case, it shows that w r ith scarcely any 

 exception the axis takes no part in the structure, all " carpophores," 

 " stylopods," &c, being simply the coherent and hypertrophied 

 margins of the carpels. 



Similarly the free-central placenta of Primulacece received its in- 

 terpretation as being coherent and ovuliferous bases of five carpels 

 which have the upper parts of their margins cohering in a parietal 

 manner and without ovules. 



The illustrations are of about sixty genera, and nearly twenty 

 orders. 



The author proposes continuing his observations. 



III. u The early Stages in tlie Development of Antedon rosacea." 

 By H. Bury, B.A., F.L.S., Scholar of Trinity College, 

 Cambridge. Communicated by P. Herbert Carpenter, 

 D.Sc, F.R.S., F.L.S. Received December 7, 1887. 



(Abstract.) 



The materials for this study were obtained from Naples in the 

 winter of 1886-87. In the orientation of the larva, J. Barrois' 

 suggestion ('Comptes Rendus,' November 9th, 1886) has been adopted, 

 viz., that the stalk of the pentacrinoid represents the praeoral lobe of 

 other Echinoderm larvae. 



Development. 



External Form. — Segmentation is regular, and a gastrula is formed' 

 by invagination. The blastopore closes early and the larva gradually 

 elongates. Ciliation is at first uniform, but soon an anterior tuft of 

 cilia and five ciliated bands become visible, and the intermediate cilia 

 disappear. The anterior ciliated band is incomplete ventrally, and is 

 either absent in the British form or escaped Wyville Thomson's 

 notice. Two ciliated depressions also appear on the ventral surface. 

 The anterior one (" pseudoproct " of W. Thomson) may be cnlled the 

 "praeoral pit;" and the posterior one (" pseudostome ") the ''larval 

 mouth." The "yellow cells" (green by transmitted light) appear 



