50 
CoBBOLD, on Actinotroha. 
ceans and molluscs as demonstrative of the manner in which 
it is produced, as in the artificial specimens, still these 
occurring in contact with living structures, would always 
have left a doubt as to what part of the phenomenon was due 
to vital and what to physical agency, and thus the question 
would have remained a debateable one. And certainly the 
cytoblast theory of Schwann and others — the very founda- 
tion-stone of modern histology — would have contributed 
nothing towards the solution of this difficulty, or ever have 
led to the discovery of the fact, that the process of calcifica- 
tion in the shell of a crab or an oyster is a directly physical 
one. 
On a Probably New Species or Form of Actinotrocha, 
from the Frith of Forth. By T. Spencer Cobbold, 
M.D.,F.L.S., Lecturer on Botany at St. Mary's, London. 
(Read at the Microscopical Society, December 9th, 1857.) 
In the autumn of 1856, I procured from the south shore 
of the Frith of Forth, near Portobello, three examples of an 
animalcule, which, on microscopical examination, at once re- 
minded me of Miiller's Pluteus paradoxus, and other allied 
forms of echinoderm-larva described by him in the later 
volumes of the Berlin Academy's ^ Transactions.^ However, 
on recently going over these various memoirs, and comparing 
his figures with those here reproduced (Plate IV, figs. 10, II, 
12), I felt inclined to doubt the correctness of my original 
conception of its larval condition, and was thereupon induced 
to assume that it might with greater propriety be referred 
to the group of Polyzoa. 
Although it should be fully proved to be a true echinoderm- 
larva, the remarkable analogy subsisting between Professor 
AUman's typical polyzoon and the creature under considera- 
tion, must be apparent to the most superficial observation. 
Commencing from above, the following parts may be recog- 
nised. In the first place, we have an enormously developed 
epistome, forming a kind of beak, which when closed or shut 
down rests upon a slightly convex lophophore. The latter is 
armed with numerous tentacula, clothed with highly active 
vibratile cilia, and is succeeded by a more or less funnel- 
shaped body, terminating abruptly at the caudal end. The 
margin of this disciform extremity is occupied by a slightly 
projecting ciliated band, and the anal orifice is placed in the 
centre. The stomach and intestine, though simple and con- 
tinuous, are distinct from each other, and traces of additional 
viscera may be recognized. By reflected sun-light the tissue 
of the ciliated band is seen to contain a number of highly 
refracting corpuscles of a golden yellow colour. 
