43 



as A. brownei. The fact that the latter was got off the west coast 

 of Ireland points to a drift of an oceanic character. 



All this may be said to be vague and not scientific, but does 

 it add to clearness and is it any more scientific to keep on tagging 

 specific names to every seeming variety which comes into the 

 hands of the collector ? The Phoronidea is not the only group 

 which suffers from this practice. 



Strictly speaking, the group should be called the Actino- 

 trochidea, and the genus Actinotrocha, but as no one can estimate 

 the time it will take to finally resolve the relationships of the 

 larvae to the adults, I venture to suggest that Phoronis be finally 

 adoiDtecl as the generic name, with Phoronis hippocrepia as the 

 genotype. 



4._DEVEL0PMENT AND STRUCTURE. 



I do not intend to give a detailed account of the structure, 

 for the work I did so many years ago will have to be relegated to 

 the scrap heap from the papers which have been published since, 

 but I do not think that even Goodrich will find fault with me for 

 saying that I saw and sketched the solenocytes and had called them 

 excretory cells. I shall content myself with giving here a summary 

 of the important facts of development, of the structure of Actino- 

 trocha, and of the changes produced at metamorphosis. 



1. Development. — The early development takes place in 

 the tentacular cro^vn as a rule. Total segmentation leads to the 

 formation of a blastula, and a gastrula is derived by invagination. 

 According to de Seh-s Longchamps the lips of the blastopore fuse 

 posteriorly and the anterior end persists to become the mouth. 

 The whole blastoporal area, however, is involved in the stomodeal 

 invagination. Mesenchyme is developed from the entoderm as 

 isolated cells. Ultimately there arise therefrom (1) a blastocoele 

 which occupies the pre-tentacular zone of the body of the larva — 

 the oral field region indicated by shading in Fig. 1 including 

 the larval tentacles ; (2) a narrow body cavity — the lopho- 

 phoral cavity — which is associated with the adult tentacles ; (3) 

 the trunk body cavity which occupies the post-tentacular region 

 of the body. The mesoderm also gives rise to blood vessels and 

 blood cells. 



