492 SUMMARY OF CURRENT RESEARCHES RELATING TO 



heart ; and (G) details of mantle innervation and pallial tentacles. We 

 have used the memoir in an advanced class and have found it most 

 serviceable. 



Function of Subradular Organ in Chiton.* — H. Heath has made 

 observations on the protrusion and use of the subradular organ in 

 Cryptochiton stelleri. The organ in question is situated at the bottom 

 of the subradular sheath formed by the backward prolongation of the 

 hinder wall of the mouth-cavity. It is a bilobed structure that has 

 been aptly compared to two beans with their concave surfaces in contact. 

 Its outer layer, bounding the mouth-cavity, consists of the buccal epi- 

 thelium modified at this point into high and ciliated columnar cells, 

 usually pigmented and differentiated into sensory and supporting cells. 

 The remaining portions of the organ consist of numerous muscle and 

 connective-tissue fibres, that in addition to their other functions afford 

 lodgment for the relatively well-developed subradular ganglia. 



From the observations, it appears that the food and probably the 

 nature of the object on which the animal rests is determined by tactile, 

 and perhaps olfactory organs situated on the proboscis ; while the sub- 

 radular organ is a structure used exclusively for testing the character of 

 the food, in all likelihood gustatory in function. 



Follicular Cells in Gonads of Gastropods. f — C. de Bruyne shows 

 that in Prosobranchs the structure of the gonads in the two sexes is 

 absolutely parallel. In both, there are follicular cells, of homologous 

 structure, which fill a nutritive role and serve also for protection or 

 fixation. These follicular cells, like the spermatogonia and oogonia, 

 arise from an " indifferent " germinative tissue. The nutritive or 

 follicular cells, in Paludina for instance, have the same origin as the 

 distinctive sex-cells. The same is true of the hermaphrodite Pulmonates. 

 " The follicular cells are neither abortive sex-cells, nor ancestors of the 

 ova and spermatozoa, nor residual elements ; they are constituent ele- 

 ments of the gonads which have a vegetative, — and perhaps mechanical 

 role." 



Aeriferous Canal in Shell of certain Pulmonata.J — A. Bavay 

 directs attention to the presence in small Cyclophorida? (allied to 

 Opisthoporus, Spvraculum, and My cams) of an aeriferous canal within, 

 the shell, opening internally, but not externally. 



Synopsis of Palsearctic Forms of Clausilia.§ — C. A. Westerlund 

 has studied the numerous forms of this type of snail. His general 

 heading runs : — CI. I. Malacozoa Cephalophora. Order I. Inoperculata. 

 Section 1, Monotrema. Subsection 2, Gnathophora. Family Helicida?. 

 Subfamily 2, Pupina. The type Clausilia includes Balea Prid., Clausilia 

 Drap., Laminifera Bttg., and Serrulina Mss. The strict genus Clausilia 

 includes 33 subgenera ! 



'& v 



* Anat. Anzeig., xxiii. (1903) pp. 92-5 (4 figs.). 

 f Bull. Classe d. Sciences Acad. Belg., 1903, pp. 115-35. 

 % Bull. Soc. Zool. Fiance, xxviii. (1903) pp. 140-3. 



§ Mem. Acad. Imp. Sci. St. Petersbourg, xi. No. 11 (1901, received 1903) 

 pp. xxxvii. and 1-203. 



