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ELISHA MITCHELL SCIENTIFIC SOCIETY. 59 
nately Wilson was unable to make out anything as to the 
connection of the sensory plate with the ganglia. The 
sense organ above the gill cleft, although differentiated, 
is a larval structure only, and disappears in the adult’’ 
(quoted from Locy lc. p. 548). | | 
Locy writing on elasmobranch development (A895, ie.) 
goes on to show the advance of our knowledge in this 
matter 
tain in some elasmobranch forms. Mitrophanow in 1890 
‘‘A quite similar condition is now known to ob- 
published a preliminary report of his observations on the 
lateral line-of Acanthias and other elasmobranchs. In 
1893. he published a full report of the same, illustrated 
by many figures. He describes a continuous thickening 
of the epidermis along the sides of the head, embracing 
the territory of the roots of the seventh to tenth nerves. 
From this thickening there is separated the material for 
the auditory saucer, the branchial sense-organs, and the 
beginning of the lateral line. My observations on this — 
region in Squalus agree with those of Mitrophanow.” 
Locy’s observations are briefly described further on in his 
paper (p. 517), the author mentioning that “a considera- 
tion of the so-called branchial sense-organs and_ their 
ganglia is reserved to be published later.’ } 
The discovery that the common anlage was not a pecul- 
iar feature of a teleost species, but existed in widely dif- 
ferent Ichthyopsida (Mitrophanow" describes the anlage _ 
not only for selachians, but for teleosts, cyclostomes, and — 
amphibia as well), indicated that the point was one worth 
tollowing up. 
The Serranus egg is a small, pelagie egg. In it the 
common anlage is more sharply differentiated from the 
general ectoderm, than in the selachian and cyclostome 
forms studied by Mitrophanow and Locy. In Serranus” 
the anlage is a furrow, in the latter forms it isa thicken- 
>) 
®Eitude embryogéniqute sur les Sélaciens. Arch. de Zool. exp. et gen 
1893. 
