64 H. V. NEAL 



Gast ('09, p. 428) expresses himself as agreeing with Dohrn 

 that primary paths do not exist for the oculomotor. His obser- 

 vations confirm those of Harrison ('07) that the first fiber anlagen 

 are amoeboid and those of the oculomotor are the processes of 

 medullary neuroblasts. 



In disproof of the view that the oculomotor is primarily con- 

 nected with its muscle, Belogolowy (10, p. 366) mentions the 

 fact that in embryo chicks a transient branch of the oculomotor 

 extends to the external rectus muscle, later innervated by the 

 abducens. Belogolowy is unable to reconcile the presence of this 

 transient and aberrant relationship with the doctrine of the fixed 

 and unchangeable relationship of nerve and muscle. 



According to Filatoff ('07) the oculomotor anlage appears in 

 Emys primarily as a cellular strand extending from the myotome 

 of VanWijhe's first somite toward the base of the midbrain. 

 Filatoff, therefore, infers the primary connection of nerve and 

 muscle. Johnson ('13), however, finds that in reptile embryos 

 the anlage of the pculomotorius becomes secondarily connected 

 with its myotome. " Filatoff 's conclusions are not applicable to 

 Chelydra." 



b. What cells contribute to the formation of the protoplasmic con- 

 nections between midbrain and somite 1 f According to Miss Piatt 

 ('91), Mitrophanow ('93) and Sedgwick ('94) protoplasmic con- 

 nection between midbrain and somite 1 is initiated by a pro- 

 liferation of cells from the mesocephalic ganglion toward the 

 brain. According to Sedgwick this migration is accompanied by 

 a differentiation of a pre-existing syncytial strand. Ziegler ('08) 

 also infers the centripetal growth of the oculomotor, on the 

 basis of the evidence that in a 25 mm. embryo of Chlamydose- 

 lachus the oculomotor "has not extended its growth as far as 

 the floor of the midbrain." Since the oculomotor nerve makes 

 its first appearance in a 9-10 mm. selachian embryo and con- 

 nection between brain and somite is already established in a 

 10 mm. embryo, Gast is undoubtedly correct in inferring that 

 the oculomotor anlage in Ziegler's specimen was ruptured through 

 shrinkage and that his- inference is consequently fallacious. Miss 

 Piatt, Mitrophanow, and Sedgwick were also dealing with ad- 



