206 
proof of a fusion of the watervascular system of the two spec- 
imens which was not to be expected either. 
As far as I know, this case has not before been mentioned to 
occur among Holothurians in nature. Something similar has been 
noted by Monticelli who, in the aquarium, has seen two pieces 
of skin from Cucumaria planci (Brandt) fuse together. 
The faet that the coalesced specimens are in different positions 
to one another, as seen in the figure, is in good accordance with 
the way in which the coalescence occurs, the position in which 
the specimens attach themselves being, of course, quite accidental. 
III. 
The species Actinopyga parvula (Sel.) is stated to have a re- 
markably wide distribution. Théel („Challenger“ Holothurioidea, 
p. 199) gives only the type locality, Florida, but in later works 
it is recorded from various places in the Pacific (Fisher, Erwe, 
Bed for d). At the same time the species Miilleria flavo-castanea 
Théel from Madeira is made a synonym of parvula. Théel him- 
self is of opinion that perhaps the flavo-castanea is the adult par¬ 
vula, and later on all authors have taken this as a faet. 
Already from a geographical point of view this distribution 
seems remarkable enough to arouse suspicion as to the identific- 
ations. Of course, such a cosmopolitan distribution cannot beforehand 
be denied, we have for instance in Amphipholis squamata (D. Chiaje) 
an Echinoderm, which seems to be really cosmopolitan; in other cases, 
however, — f. i. Diadema setosum Gray, — this worldwide distribution 
has proved to rest on wrong identifications. — I have then under- 
taken a careful study of the material of Actinopyga parvula at my 
disposal. Through the assistance of Dr. Th. Mortensen I have 
been able to examine one of the type specimens of Selen ka’s 
A. parvula, received from Prof. Ehlers, Gottingen, the type of 
M. flavo-castanea Théel, received from Prof. T h. O d h n e r, Stock¬ 
holm, together with specimens identified by Théel as H. captiva 
Ludwig, from Prof. Hartmeyer, Berlin; the specimen from Au- 
stralia, identified by W. Erwe as A. parvula, was received from 
