92 WILLIAM BATESON. 
Another feature which ought not to be overlooked in a 
general account of this species (B. Kowalevskii) is its extreme 
vitality. In a bucket of unaérated water in which all other animals 
had died some days before, in a hot climate, these creatures were 
able to carry on their existence, and parts of the body may be seen 
moving about by means of the ciliated skin to which a com- 
pletely macerated skeleton of the branchiz is attached. Lobes 
of the testis, torn off, will likewise swim about for days. To 
what extent the body is capable of regeneration I cannot say. 
Specimens were found in which there was at all events an 
appearance suggesting that the proboscis had grown again. 
Spengel has alluded to regeneration of tissues as occurring in 
B. minutus, and I have little doubt that it is also common in 
B. Kowalevskii. 
With regard to the specific name of this form, it appears 
that the figure and description given by Agassiz of B. Kowa- 
levskii identify it with the form which is the subject of this 
paper. The mode of development ascribed by him to the 
species is of course entirely different. Seeing, however, that 
he was unable to show the connection between the animals 
found by him in the beach and the Tornaria which he reared, 
it does not seem by any means certain that these Tornaria 
were the larve of B. Kowalevskii. On the whole, it is 
at least possible that they were the young of some other 
species, e.g. B. Brooksii, which occur at least as far 
north as the Chesapeake, and probably higher still on the 
coast. 
From a general survey of the group Enteropneusta, which I 
hope subsequently to attempt, I think it will appear likely that 
B. Kowalevskii stands, in many respects, in a group differing 
in several features from the other members, which agree with 
one another in these points, e.g. short proboscis, complicated 
branchial skeleton, operculum small, liver saccules present, eggs 
minute, &c. It is to the latter division I am inclined to 
believe that Tornaria alone belongs. 
In studying. the anatomy of Balanoglossus by means of 
sections difficulty arises owing to the variable amount of con- 
