52 
CoBBOLD^ on Actinotrocha. 
the same generic type. In the absence^ however^ of more 
precise knowledge than we at present possess^ of the growth 
and development of these creatures, it is perhaps premature 
to ofPer any speculations upon its true relations. And, as 
suggested by Gegenbaur, with respect to the Actinotrocha de- 
scribed by him, the dilFerences in the forms already noticed 
may be due to their having been observed in different stages 
of growth or development. The general opinion seems in- 
clined to regard Actinotrocha as a larval form of some kind, 
and most probably of an echinoderm. Amongst those who 
have entertained this opinion, I would adduce Yon Siebold,who 
compares Actinotrocha with a Bipinnaina from which the per- 
fect asterid has become detached (Wiegmann's Archiv,' 
1850.) At present we cannot be surprised that the true re- 
lations of this creature should be very obscure, but may 
remember that in the same paper in which J. Miiller notices 
Actinotrocha, he for the first time describes a Pluteus, without 
then having any comprehension of its marvellous relations to 
the Echinodermata, subsequently ascertained by his unwearied 
researches in that and other allied forms — researches which 
have added so immensely to natural knowledge, and contri- 
buted another imperishable wreath to the well- won fame of 
the illustrious physiologist. 
\_Note. — At the meeting of the Microscopical Society, at 
which the above paper was read. Dr. Carpenter exhibited a 
specimen of Actinotrocha (apparently A. branchiata, Miiller) 
preserved in dilute glycerine, and the inspection of which further 
confirmed the opinion above expressed, that the form described 
by Dr. Cobbold differed from that species in several impor- 
tant particulars, and more especially in the shape of the hood 
or epistome, and in the number of tentacles around the body. 
Dr. Carpenter also stated that the form shown by him was 
extremely abundant in the Isle of Arran, and probably else- 
where, so that it is to be hoped that opportunities will be 
taken to search for and examine this and allied forms, at 
diflPerent seasons of the year, on various parts of the coast. 
—Eds.] 
