368 



E. KAY LANKESTER. 



With regard to the shell-gland, which has not up to the 

 present moment been recognised by any observers, my studies 

 have yielded most interesting results. This organ appears 

 to have a very wide distribution among the different classes 

 of Mollusca, and to be present even in the most remote 

 members of the group — the Polyzoa and Brachiopoda. 



I do not propose here to give a detailed account of this 



Firf J. 



' ■ ( 11 



A 



■^^-r iW^. 



Diagram of an embryo of Fmdium pusillum. f. Foot. m. Mouth, ph. 

 Pharynx, gs. Gastrula-stomach (now bilobed). pi. Pedicle of in- 

 vagination (terminal intestine), slm. Shell-gland. 



Diagram of an embryo of Pleurobranchidmm. f. Foot. ot. Otocyst. tn. 

 Mouth. V. Velum, tig Nerve-ganglion, ry. Residual yelk-spheres. 

 shs. Shell-gland, i. Intestine. 



