272 BASHFOGD DEAN. 



As Price has shown, and as others have indicated, the 

 development of a Myxinoid is typically raeroblastic ;^ it might 

 reasonably be surmised that the large amount of yolk-material 

 would enable the embryo to attain an advanced stage before 

 the period of hatching, and that the duration of development 

 in the egg should be a long one. These conjectures are 

 clearly confirmed by the writer's observations upon embryos 

 reared for a time in aquaria ; he believes that the eggs do not 

 hatch within two months, and thinks it possible that several 

 more months may be taken. By this time the young Bdello- 

 stoma has attained a length of over 6 cm., and has outwardly 

 the characters of the adult. Price notes that a distinctly 

 larval period is absent. 



There can be little doubt, as Price has noted, that Bdel- 

 lostoma is not protandric in the sense demonstrated by 

 Cunningham in Myxine.^ The eggs are in all probability 

 fertilised after deposition. An egg nucleus is then present 

 immmediately below the single large raicropyle at the opercu- 

 lated (animal) pole of the egg. 



Segmentation. — Until the writer's material of the 

 youngest stages shall have been sectioned, he can refer but 

 doubtfully to a single egg. Of this transverse sections near 

 the animal pole show on one side a number of nucleus-like 

 structures embedded in a clear peripheral germinal area. 

 There are no cell outlines, although the stage is probably 

 early. One cannot doubt, however, that a condition of asym- 

 metry with reference to the longitudinal axis of the egg 

 appears in very early stages. And from the conditions of the 

 following embryo it will be inferred that the dorsal lip of the 

 blastopore appears on one side of the egg, not far from the 

 rim of the opercule, and that from this region it closes fissure- 

 wise backward. 



Very Early Embryo (fig. 3). — At this stage the embryo 

 is thread-like. The very narrow neural cord, n, represents 



» Cuuniugham, Retzius (1889), 'Biol. Foren. Forhdgr.,' Bd. i, pp. 22-28. 

 ^ Cunningham, J. T., "Reproductive Elements in Myxine," 'Quart. 

 Journ. Micros. Sol.,' vol. xxvii, 1886. 



