600 
F. H. EDGEWORTH. 
In the rabbit and pig there is no stage in which the 
temporal muscle is inserted solely into the upper edge of the 
Anlage of the mandible ; its cells become spindle-shaped before 
it spreads downwards^ with a forked extremity, on either side 
of the Anlage of the mandible. 
The formation of the coronoid process of the mandible 
takes place in Dasynrus after ossification has begun, in the 
rabbit and pig in the Anlage stage. In all three animals the 
process is formed by a dorsal extension into an already formed 
muscle or mnscle-Anlage. 
The stages of Ornithorhynchus and Echidna available did 
not permit of observations on the development of the indi- 
vidual muscles formed from the lateral masticatory muscle. 
_ M a s s e t e r and Z y g o m a t i c o - m a n d i b ul a r i s . — In many 
Mammals a zygomatico-mandibularis is differentiated between 
the temporal and masseter muscles. Allen, who first described 
the muscle, in man, considered it to be a separated deep 
portion of the masseter, whilst Toldt held that it is derived 
from the temporal. Toldt stated that “ er stammt von der 
Muskelfasergruppe her, welche die oberflachlichste Schichte 
der nrspriinglichen Anlage des Schlafenmuskels darstellt und 
von jeuer Mesodermschichte kommt welche sich bleibend zur 
Fascia temporalis gestaltet. Da sich in derselben Mesoderm- 
schichte spater das Jochbeiu, beziehungsweise der gauze 
Jochbogen entwickelt, so tritt ein bestimmter Auteil der 
bezeichneten Fasergruppe mit der medialen Flache des 
Jochbogens in Beziehuug, d. h. er nimmt von dieser bis an 
ihren unteren Hand herab bleibend seinen Ursprung. Er 
steht demgemass an seinen Ursprung mit dem Schlafenmuskel 
in ununterbrochenen Zusammeuhang, hat aber durch die 
erworbene Beziehuug zum Jochbogen einen besonderen 
Character erlangt.^^ 
In Dasyurus, as detailed above, the masseter muscle is 
proliferated, in stage C, downwards and backwards from the 
anterior ventral edge of the lateral muscle on the outside of 
the mandible ; and from that time onward can be distinguished 
in transverse section by the direction of its fibres. The 
