MISCELLANEOUS NOTES. 



67 



form, of the £>rocess wffecthtg tlie homologous parts in Elusmobriuichit "■ 

 (p. 88)." 



Also " It seems most reasonable to conclude that in coarse of phy- 

 logenetic development, the yolk which is homologous with the yolk-mass 

 of the Elasmobranch egg must have dwindled in size and been lost 

 from the eggs of the ancestors of the Amniofca. This yolk-mass which 

 I may call the primary yolk-mass has, however, left in some eggs (e. g. 

 in the Chelonian egg) its rudiments in the structure known as the primi- 

 tive plate and its direct derivative, the problematical cell mass* behind 

 the blastopore. In further course of development, the eggs of the 

 ancestors of the Amniota acquired for the second time a large yolk-mass 

 which I may call the secondary yolk-mass. It is this which we see in 

 the Amniota eggs of the present day. * * * Thus it becomes im- 

 perative to distinguish the meroblastic egg of the Elasinobrancnii from 

 the meroblastic egg of the Amniota. The former may be called the 

 primary meroblastic ovum or proto-meroblastic ovum and the latter the 

 secondary meroblastic ovum or meta-vieroblast ic ovum " (p. 90). 



Comparisons are also briefly made with the processes seen in Am- 

 phibia, Aves and Mammalia. 



Finally, the classification of the vertebrate eggs is made as follows : — 



I. Primary Type, (a) Archi-Holoblastic (Amphioxus), (h) Proto- 

 Holoblastic (C3 r clostomi), (c) Proto-meroblastic (Elasmobranchii, Teleostei) 

 (d) Meso-holoblostic (Amphibia ?). 



II. Secondary Type, (a) Meta-meroblastic (Beptilia, Aves), (b) 

 Meta-Holoblastic (Mammalia). 



In a postscript, Will's article " Die Anlage der Keimblätter bei 

 der Eidechse (Eacerta) " Zoo/. Jahrb. Abth.f. Anat. IX. Bd. is reviewed. 



K. MiTSUKURr. 



A Living Specimen of Pleurotomaria Beyrichii. By the kind- 

 ness of Alan \vs ton, Esq. of Yokohama we were favored, on the 31st of 

 March last (1HU7), with a view of a living individual of that rare mollusk, 

 Pleurotomaria BeyricJiii. The specimen had been received by him, the 

 day before, and had probably been caught by a long-line at the Okinosé 

 Bank off Boshü. The animal was not very lively and could not be 

 persuaded to extend itself fully. At the utmost, we were able to see the 

 foot and a part of the head. The sole of the foot was straw-yellow. 

 The side of the foot and the throat were mottled with large and small 



* I. e. the " £olfc-plug. : 



