CURRENT LITERATURE. 27 



researches, on the most noteworthy examples of shell formation among the 

 Mollusca. To this end he passes in review the researches of previous writers 

 on (i) the intimate structure of the shells of Aiiocloufa, Pinna and Mclcagriiui , 

 (2) the origin of the "prisms" in Anodonta ; (3) the physical and especially the 

 optical characters of the " prisms " and pearly-layer ; (4) the intimate structure 

 of the Gastropod shell ; (5) the character and growth of the Gastropod shell ; 

 and finishes with a lengthy summary. 



In the concluding paragraphs of the summary he points out that the 

 deposition of carbonate of lime on the part of an animal organism is less than 

 ever to be regarded as the result of a simple chemical reaction, but is manifestly 

 a question of highly complicated chemical processes on the part of Jiving cells 

 without, however, a direct formative influence on the part of the latter. It is 

 further beyond doubt that each shell layer having a special structure arises as 

 a specially constituted secretion derived from special cells : the conditions 

 under which these characteristic structures arise is at present by no means 

 sufficiently clear, but have nothing to do with any albuminoid replacement 

 consequent on putrefaction. 



In a subsequent paper the author intends to treat of the artificial production 

 of shell-structure. 



We have failed to find anything new in this treatise which, however, 

 appears to form an admirable summary of the present state of our knowledge on 

 the subject of molluscan shell structure, and as such to be of value. The plates 

 which illustrate it reproduce many familiar figures, and there is a useful little 

 bibliography, which, however, is not, and evidently does not pretend to be, as 

 complete as that given bj' Moynier de Villepoix, whom the author cites, or by 

 Dr. Stempell (Biol. Centralbl., Bd. xx.), to whose interesting and important 

 paper, the author strangely enough does not allude. — B. B. Woodward. 



Kowalevsky, A. — Sur le genre Cliactoih-rnm. Arch. Zoo), exp. et gen., 1901 

 (s. 3), T. ix., pp. 261 — 283, pi. X — xii. 



Tiie author describes two exceedingly interesting new species of 

 Chactodcrnia, dredged in the Sea of Marmara. The first, C. radulifcra, is 

 characterised by a complex radula, bearing nine rows of teeth, which is 

 described and figured in great detail. The second species, C. giitturosum, so 

 named from a curious habit it has of inflating the head-region, which aids the 

 animal in burrowing, resembles externally, both C.prodiictmn and C. uitidulimi, 

 but differs from both of these species in the structure of the radula. 



Simroth, H.— Ueber die Raublungenschnecken. Naturwissensch. Woch- 

 ensch., 1901, Bd. xvii., pp. 109— 114, fig. i — 14, pp. 121 — 127, fig. 15 — 18, 

 pp. 137—140, fig. 19. 



As is well known to all malacologists, there are certain families of molluscs 

 which, according to some authors, are widely separated from one another 

 structurally, but contain genera possessing certain characteristic features in 

 common. One such group, continental malacologists have termed "Raub- 

 lungenschnecken " (Agnathous Pulmonates). 



In the present important series of papers, Dr. Simroth has brought together 

 an enormous mass of facts, and has attempted a classification of these particular 

 molluscs. Further he has put forward certain views as to the affinities of the 

 difterent genera and their phylogenetic origin, and generally summarised our 

 knowledge of numerous rare and impeifeclly known genera. 



