ANATOMY. 19 



Development of Pal. vivipara (Journ. Marine Bio. Ass., p. 139, 1821). — 

 Dr. Erlanger. 



Mollusca of Carcassone (Feu. Jeun. Nat., Jan., 1892). 



N. H. Rambles on the S.E. Coast of England (Sci. Goss., Mch., p. 54, 

 1891). — A. H. Shepherd. 



EMBRYOLOGY AND DEVELOPMENT. 



The Viviparous Nature of Balea (Journ. Conch., Vol. VI., No. 12, 1891). 

 In describing the life-history of a mollusc, recent authors have been content to 

 simply repeat the accounts of their predecessors. Happily things are changing. 

 Some years ago it was pointed out in that admirable little work of Rimmer's* 

 that Mr. Rich had stated that B. peiT'ersa, L. was viviparous, and not ovoviparous 

 as stated by Bouchard -Chautereaux. t Mr. A. E. Craven has found a number of 

 specimens among the ruins of Vianden Castle, in the Grand Duchy of Luxemburg, 

 containing two or three young specimens possessing about three whorls. We may 

 now hope to see Bouchard-Chautereaux's observations on this species omitted 

 in future accounts. 



Development of Dreissenapolymorpha(Ann. & Mag. Nat. Hist., February, 

 pp. 157-169, 1891). 



Dr. Korschelt has been studying the hitherto unknown reproduction and 

 development of this mollusc, with the immediate view of determining the presence 

 or absence of free-roving larvre, and to facilitate a later investigation of the 

 minutre of the development. 



Ova were first deposited about the middle of May, but soon perished, possibly 

 owing to the cold spring of 1891. In the middle of June ova were again 

 deposited. The method of oviposition is interesting. The valves of the shell are 

 slightly opened and quickly closed again ; each time this takes place a whitish- 

 mucous-like ball of ova is extruded. The ova contain but little yolk, and are 

 enclosed in a very delicate envelope. Segmentation is unequal, and agrees 

 generally with that of other mussels. After the widening of the primitive 

 segmentation cavity the embryo is of a roundish-oval form. The rudiment of the 

 intestine now arises from an invagination of the ectoderm, ultimately uniting with 

 the endoderm ; previous to this however, the rudiment of the shell gland has been 

 formed by an ectodermal invagination. The animal now assumes a pear-shaped 

 form, the anterior end broadens, and the cilia, present at an earlier period, become 

 more closely arranged here, forming a ciliated ring. We have now a free- 

 swimming Trochophora. After a description of the development of the velum, 

 which is bilobed and of a considerable size, Dr. Korschelt mentions that in the 

 short time he was able to devote to the younger larval stages, he did not succeed 

 in finding the primitive kidney, but its presence would appear to be almost certain 

 since Ziegler found it in Cyclas. The later stages of development are generally 

 referred to. 



ANATOMY. 



Reproductive Organs of Aplysia (Atti. R. Acad. Sci., Napoli, Vol. IV., 

 p. 1-50). 



Sig. G. F. Mazzarelli gives an account of the reproductive organs of Aplysia, 

 which he considers to be in a primitive condition, and is of opinion that the genus 

 is morphologically allied to the Cephalopoda. 



* Rimmers' Land and Freshwater Shells of the British Isles. Bogue, 1SS0. 

 t Cat. Moll. Ter. et Fluv. d. 1. D£pt. du Pas-de-Calais, p. 62, 1838. 



