204 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
which is the probable homologue of the muso. adductor mandibule of 
Selachii, to be those stated by Hatschek. ‘Whether in this muscle 
group we have to do with the muse. obliquus superior, I am not able to 
stato, since its innervation still remains uncertain tome.’ I know, how- 
ever, that it is not innervated by the oculomotorius. Its fibres, more- 
over, are not continuous with those of the velar muscle at this stage of 
development, if indeed they are at any stage. Hatschek’s chief evi- 
dence that this muscle is derived from the velar muscle apparently 
consists in their histological resemblance, which he states is complete. 
At the stage studied by me this is certainly untrue. For I find that 
while the velar muscle is composed of large fibres, at least 7 in diam- 
eter, the fibres of the muscle in question are in their widest part not 
over 3p in diameter, and also that, while the fibres of the former show 
well marked longitudinal and cross striations, those of the latter show 
these very faintly. Moreover, the nuclei of the former are for the most 
part round or oval, while those of the latter are exceedingly elongated. 
It is of course possible that Hatschek bases his statements on the exam- 
ination of the histological conditions in embryos of a different stage of 
development. But even if we grant that the muse. obliquus superior in 
Cyclostomes is, as in the Selachii, derived from the dorsal part of the 
musculature of the mandibular arch, this evidence no more warrants the 
conclusion that the muscle is splanchnic in origin in the former group 
than in the latter. Of its dorsal origin and somatic nature in the latter 
group, proof has been given above. 
Even more theoretical than his conclusions concerning the origin of 
the muse. obliquus superior appears Hatschek’s inference that the eye 
muscles innervated by the oculomotorius are derived from the con- 
strictors of the visceral arches, a conclusion which he draws apparently 
by the method of exclusion. It does not seem to have occurred to him 
that these muscles may have had their origin from the connective-tissue 
capsule of the eye, the cells of which are in my opinion derived from the 
dorsal mesoderm in this region, which in early stages becomes disinte- 
grated and surrounds the eye vesicle. Kupffer (94) thinks that the 
more difficult part of the task of tracing the development of the eye 
musculature in Ammoccetes is accomplished when he has followed the 
growth of muscle cells from the so called “ Trabekular” and the mandib- 
ular arches until they come into close relation with the eye capsule in 
1 That Hatschek (’92) incorrectly identified the musc. rectus posterior, has been 
shown by M. Fiirbringer (’97) from the study of its innervation, a matter to which 
Hatschek seems to have paid no attention, 
