256 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



desertorum, and malformed teeth have been seen in Leptaxis undata, 

 Lowe, whilst considerable variation has been noticed in Aplysia. 

 Bateson ' has collected several observations on the radula of Btwcinum, 

 showing that on the median plate the denticles may be as low as three 

 in number, or as high as nine, whilst the laterals may have from 

 three to five denticles, these latter again being sometimes unequal on 

 both sides of the radula, i.e. four on one side and three on the other. 



Of the generative organs, cases have been noticed ^ where the male 

 generative organ, which should have existed, was entirely wanting 

 {Arion hortensis, Limax Icsvis), and in Pupa musconmi a specimen has 

 been seen^ where the male organ was rudimentary and the female 

 well developed. "Whitfield* noticed that the progeny of Linmaa 

 megasoma, produced during confinement, exhibited changes in the soft 

 parts, particularly diminution and disappearance of the hermaphrodite 

 gland, which in the third generation was entirely lacking, while the 

 female organ retained vitality, and he suggests that the atrophy of 

 this caused the slenderer form which he noticed the earlier whorls 

 took. The result has been also attributed to the want of sufficient 

 and appropriate food. A case of the closing of the genital opening 

 has been noticed ^ in Helix aspersa, which has been attributed to a lack 

 of full development. The generative apparatus of Helix pomatia has 

 in one specimen been found to be divided into three entirely separate 

 groups, and other interesting, variations have been noticed.^ Parasitic 

 castration in Helix aspersa has also been recorded.'' 



Mention should be made also of the curious specimen of Helix 

 nemoralis, L., recorded by Fischer,® which was furnished on the back of 

 the foot with a fleshy cylindrical appendage, situated, when crawling, 

 just behind the shell. 



In the Pelec3q)ods some variation has been observed in the position 

 of the adductor muscles. Downing ^ found in Anodonta that in speci- 

 mens of varying ages the distance of the muscles from the umbo varied 

 considerably in relation to their distance from the shell-margin, and 

 suggested that perhaps the muscles moved less rapidly than the shell 

 grew. The anterior muscle was found to move more rapidly than the 

 posterior. 



A curious specimen of Mytilus edulis was examined by Vayssiere,^" 

 in which the valves gaped at the far end and the mantle was largely 

 developed, tilling the cavity. 



1 " Materials for the Study of Variation," p. 262. 



2 Collinge, Journ. Malac, vol. xi, p. 15 ; and see S.B. Ges. Leipzig, 1883, p. 74. 



3 Wiegniann: Jahrb. Malak. Ges., vol. v, p. 159. 



4 Bull. Amer. Mus., vol. i, pp. 29-37; cf. Troc. Boston Soc, vol. xx, and Dall, 



Bull. Phil. Soc. Washington, vol. iii, p. 75. 



5 Maugenot: Bull. Soc. Zool. France, vol. viii, p. 130. 



6 Bietrix: Bull. Soc. Philom., ser. vii, vol. x, p. 74. Semper: Reisen Arch. 



Phil., vol. V, p. 247. 

 ' Garuault: Bull. Sci. Fr. Belg., vol. xx, p. 137. 



8 Journ. Conchyl., vol. xxv, pp. 211-212, pi. iv, fig. 4. 



9 Amer. Nat., vol. xxxvi, pp. 395-400. 



1" Journ. Conchyl., ser. iii, vol. xxxix, p. 213. 



