434 SUMMAEY OF CURRENT EESEARCHES RELATING TO 



Todaropsis, Illex) ; (&) in most cases with an area of most distinct vision, 

 in which the rods are thicker and usually longer ; (c) in Chun's deep-sea 

 forms with a f ovea-like area of most distinct vision, in which the rods are 

 very long and narrow. 



£. Gastropoda. 



Eyes of Pulmonate Gastropods.* — G. Smith has made a study of 

 the morphology and histology of the eyes in several G-astropods. His 

 leading conclusions are as follows. The pigment cells of the retina of 

 Helix and Limax are indifferent, the pigment-free cells are sensory. 

 Each sensory cell gives off proximally one neurite to the optic nerve, and 

 probably one or more branched processes which attach the cell to the 

 capsule. The fibrillse of the rods are normal structures of the living 

 cell, and are doubly refractive to light. The neurofibrillse form a net- 

 work within the cell, uniformly distributed or massed into main paths 

 through it. Appearances of pigment migration in the pigment cell of 

 the retina of Planorbis trivovis were observed. 



Achatinellid Fauna of Molokai.t — Fr. Borcherding begins a 

 systematic account of the Achatinellids from this Sandwich Island — an 

 interesting study of numerous species and varieties in a relatively small 

 area. 



Structure of Acmsea testudinalis.f — M. A. Willcox publishes the 

 first part of an anatomical account of this limpet, in which he deals at 

 length with the superficial features, such as the blood-vessels seen with- 

 out dissection. 



British Nudibranchs.§ — C. Eliot communicates notes on twenty- 

 nine British Nudibranchs, including Coryphella beaumonti sp. n. and 

 Janolusflagellaius sp. n. (?). The specimen recorded in the list of British 

 forms as Berghia ccerulescens must be removed from the list, as the 

 specimen is Facelina coronata, but Staarodoris verrucosa may be added. 

 A number of other points are cleared up in the paper. 



Mutation in Molluscs. || — F. C. Baker points out that in certain 

 Molluscs, e.g. Lymncea, " the species seem to be unstable, that is, they 

 have a tendency to vary, not in a given direction, but in many directions 

 at the same time. These seem to come under the head of Mutants or 

 sports." " Where the mutation theory seems to fit in very nicely in 

 explaining the very large amount of variation in the fresh-water pulmo- 

 nates, we must not be too hasty in applying this new theory, founded as 

 it is upon plant variation, to animal life." 



5. Iiamellibranchiata. 



Natural History of Margaritifera panasesse.lf— A. W. Allen gives 

 some notes on this small oyster, which occurs in New Guinea waters. 



* Bull. Mus. Comp. Zool. Harvard, xlviii. (1906) pp. 233-84 (4 pis.). 

 t Zoologica, xix. (1906) heft 48, pp. 1-104 (5 pis. and 1 map). 

 X Amer. Nat., xl. (1906) pp. 171-87 (4 figs.). 

 § Joum. Marine Biol. Ass., vii. (1906) pp. 333-82 (2 pis.). 

 || Amer. Nat., xl. (1906) pp. 327-34 (4 figs.). 

 i Joum. Linn. Soc. (Zool.) xxix. (1906) pp. 410-13. 



