136 Victor E. Emmel. 
ciently conclusive. In the ontogeny of vertebrates, the striated mus- 
culature is evidently mesodermal in origin, but whether the same 
is true in crustacean development, especially in the case of the limb 
musculature, is not, so far as the writer is aware, clearly established. 
Consequently it seems obvious that we are not as yet justified in 
concluding that the ectodermal origin of the regenerating crustacean 
muscle is a divergence from ontogenetic development. Indeed, as 
Ost (06, p. 312) points out, it is not impossible ‘‘dass die embryo- 
nalen Muskeln von den ectodermalen Sehneneinstiilpungen aus- 
sprossten und dann Regeneration und Embryonalentwicklung sogar 
iibereinstimmten,” a conclusion which is certainly not rendered less 
improbable when one considers the degree to which the generally 
accepted conclusions regarding genetic relationships between ecto- 
derm, mesoderm, and certain forms of connective and muscle tissue 
have been called into question by the work of such investigators as 
Katschenko (88), Kolliker (’84), and Platt (798). 
b. Attachment to the Exoskeleton.—Among the first investigations 
on the attachment of the crustacean muscle is Claus’s (?86) work 
on Branchipus and Artemia. Claus concludes that in many eases 
the muscle fibers are attached directly to the exoskeleton. (pp. 22 and 
29), a conclusion which involves the assumption that among some 
invertebrates at least the muscle may be attached to the skeleton 
without the intervention of a connective tissue tendon, such as are 
typical of muscle-skeletal attachments among vertebrates. . Since 
1886 the subject has received considerable attention both for erusta- 
cea and insects, with the result that several divergent opinions have 
arisen. As far as the writer is aware, however, the problem has not 
been studied from the standpoint of regeneration; consequently data 
derived from the present investigation of the lobster may not be 
valueless. 
Attention has already been directed to the fact that in the early 
stages of the regenerating bud and up to the time when the muscle 
fibrils have become well differentiated, there is no definite boundary 
between the outer epithelial cells related to the chitin and the internal 
cell mass in which muscle develops. Cell walls are not evident, and 
the cytoplasm of the two regions appears syneytially related, the 
