290 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Mollusca. 

 y. Gastropoda. 



Studies of Gastropod Shells.* — Amadeus W. Graban regards the 

 present geological period as that of the acme of Gastropods. What 

 Jurassic and early Cretaceous ages were to the Cephalopods, the Tertiary 

 and present periods are to the Gastropods. This is indicated not only 

 by the great number of species, but also by the fact that so many series 

 have branched out into bizarre types, in which excessive development of 

 spines and tubercles suggests that the limit of variation is approached. 

 Phylogerontic types are furthermore to be found in the majority of 

 series, while some groups, such as Strombus, Cyprcm, &c. are represented 

 only by phylogerontic forms in the modern seas. 



The author contributes very interesting short studies on the pro- 

 toconch of Gastropods, the ornamentation of the protoconch, septa in 

 the apex of Gastropods, the characteristics of the conch, the varices, 

 other ornamental features, individual old age and phylogerontic charac- 

 ters in Gastropods, illustrations of the law of tachygenesis and of 

 parallelism among Gastropods. He sums up the result of his studies 

 in the words of Hyatt's law of morphogenesis : " A natural classification 

 may be made by means of a system of analysis in which the individual 

 is the unit of comparison, because its life in all its phases, morphological 

 and physiological, healthy or pathological, embryo, larva, adolescent, 

 adult, and old (ontogeny), correlates with the morphological and physio- 

 logical history of the group to which it belongs (phylogeny). 1 ' 



Kidney of Helix pomatia.f — G. Stiasny gives a detailed account of 

 this organ, in regard to which many, if not most, text-books have made 

 erroneous statements. He distinguishes the kidney proper, the primary 

 ureter, which extends from an opening at the apex of the kidney to the 

 posterior corner, and the secondary ureter which runs from the posterior 

 corner of the kidney to the external aperture. 



Sense of Smell in Snails. $ — Emile Yung has made experiments 

 with snails and slugs as to their sense of smell. He notes that the seat 

 of the sense has been sought on the long-horns (near the eye), on the 

 short horns, about the lips, at the pulmonary opening, in the vicinity of 

 the pedal gland, and so on. The fact is that the general surface of the 

 skin is sensitive to strong odours, and both pairs of horns especially. A 

 snail deprived of its horns still finds its food and behaves as usual. The 

 sensitiveness in all cases has a very short radius. 



Purple of Purpura lapillus.§ — A. Letellier gives a short account of 

 the researches which have been made on the " purple " of the dog-whelk, 

 and re-expounds his own results. He has found in the secretion three 

 distinct bodies — a yellow substance which does not change on exposure 

 to light, and two kinds of green substance, one changing quickly to 

 blue in sunlight, the other becoming carmine red. The combination of 

 these three substances gives a coloration first yellow, then green to blue, 



* Amer. Natural, xxxvi. (1902^ pp. 917-45 (18 figs.). 



t Zool. Anzeig., xxvi. (1903) pp. 334-44 (5 tigs.). 



t Arch. Sci. Pliys. Nat., xiv. (1902) pp. 586-7. 



§ Arch. Zool. Exper., i. 4th series (1903-) Notes et Revue, No. 2, pp. xxv.-ix. 



