XIV Proceedings of the Association of American Anatomists 
4. Certain instances of Sternales, occurring in direct combination 
with additional supernumerary muscles, of undoubtedly pannicular 
origin, may possibly represent reversions of the cuticular muscle. More 
probably, however, they are to be interpreted as examples of coincidence 
of several etiological factors simultaneously operative in the same 
individual. . 
5. The muscles forming the deep group result from faulty processes 
in the cleavage of the pectoral mass, while their secondary attachments 
vield the subvarieties noted. 
THE EVOLUTION OF THE FLEXOR SUBLIMIS DIGITORUM. By JAmzs 
PLAYFAIR McMurricu. University of Michigan. AMERICAN JOURNAL 
oF ANATOMY, VOL. II, No. 2. 
NOTES ON THE HISTOGENESIS OF THE STRIATED MUSCLE IN 
NECTURUS. (Communicated by LEWELLys F. BARKER.) By ALBERT 
C. EycLesHyMER. Harvard Embryological Laboratory and Hull Labora- 
tory of Anatomy, University of Chicago. 
The myoblasts in the earliest stages (5-7 mm.) form a more or less 
complete syncytium; i. e. there are cytoplasmic strands connecting the 
ends of myoblasts in adjoining myotomes. After the septa are formed 
through the ingrowth of the mesenchyme these strands are no longer dis- 
cernible. ) 
The myoblasts in all stages correspond precisely in length to the 
respective lengths of the myotomes from which they are taken. It is 
therefore improbable that in this form a number of myoblasts, in adjoin- 
ing myotomes, unite to form a single muscle fibre as observed by God- 
lewski in the rabbit. 
The first change in the myoblast preparatory to fibrillation is an accel- 
erated absorption of yolk granules in either end of the myoblast which 
gives rise to clear, yolk-free zones. In the clear zones which have thus 
arisen, longitudinal striew are soon differentiated. These striz are first 
formed on the notochordal side of the myoblast and in the 7 mm. em- 
bryo converge in such a manner that they take on a somewhat conical 
or brush-like arrangement. The bases of these cones, or brushes, spread 
over a considerable portion of the end of the myoblast while their apices 
lie on the notochordal margin. 
These striz are the beginnings of the fibrillee proper, but at first show 
no transverse markings whatever. Pari passu with the absorption of 
yolk granules these cones of fibrilla rapidly extend, each toward the other 
until, in the 8 mm. embryo, they have united and have given rise to a 
continuous tract on the notochordal side of the cell. The entire tract 
