No. 3.] MUSCLES AND NERVES I[N AMIA CALVA. Fees 
little pieces of cartilage described by Gegenbaur in Cestracion 
(quoted No. 48, p. 154). 
For the dorsal processes of Amia Baur gives no name, and 
I find no description, that I can satisfactorily identify, of such 
processes in any fish or other animal. They may be centra or 
pleurocentra, or the interarcualia of Klaatsch in Chimaera 
(No. 64, Aédstr.), or possibly the basi-dorsals of Gadow and 
Abbott (No. 39). They are certainly not rudimentary dorsal 
arches (Schmidt), nor can they be considered as the proximal 
ends of dorsal arches, for they are segmented, after the forma- 
tion of those arches, from a continuous cartilaginous layer, or 
« Anlage,” and they lie, in larvae, between the dorsal arches. 
The arches themselves are certainly neuropophyses, but they 
are not, in their origin, processes of the vertebrae. The whole 
subject is to me much too obscure to venture upon names. 
The dorsal portions of the anterior intermuscular septa, in 
larvae of Amia, differ considerably, in their relations to the 
vertebral processes, dorsal arches, and dorsal spines, from what 
has been described in the adult. In 12 mm. larvae they run 
downward and forward along the antero-lateral edges of the dor- 
sal arches, then turn sharply forward, practically at a right angle, 
as is well shown in vertical sections, onto the dorsal process 
in front of the arch to which they belong, and then downward, 
at a right angle again, onto the corresponding lateral process 
and rib. Ventral to the rib they turn backward, and seem to 
have their attachment, or origin, in the region where, later, the 
crest between two constrictions of the notochord will appear. 
They are thus, at this age, restricted to a single dorsal arch, 
and are, in their central portions, vertebral in position. In 
their dorsal portions they are intervertebral in position, as the 
dorsal arches themselves are. 
Between the age represented by 12 mm. larvae, and the adult, 
there must, therefore, have been a gradual backward displace- 
ment of the middle portion of that part of each of the anterior 
intermuscular septa that lies above the level of the vertebral 
column, the displacement becoming continually more pronounced 
up to its complete development. The amount of this displace- 
ment certainly varies, not only at different ages, but also in 
