94 CURRENT LITERATURE. 



the creature is still within the test, and cannot therefore be foreign bodies. The 

 paper is illustrated by five excellent plates. — K. H. BuRNF.. 



MeisenheimeP, J. — Entwicklungsgeschichte von Dreissensia polymorpha Pall. 

 I. P.is zur Ausbildung der jungen Trochophoralarve, pp. 44, 2 folding plates. 

 Marburg: 1899. 



The author points out that amongst the freshwater mussels Dreissensia poly- 

 morpha occupies a remarkably isolated position, inasmuch as in structure and 

 development it clearly shows the characters of a marine form. He traces the 

 history of its distribution in Europe from before the ice-age. when it was apparently 

 widely distributed throughout North Germany, to the present day when it has 

 spread over the greater part of Europe north of the Alps and the Pyrenees. It 

 seems to have entered England in 1824. 



While in some freshwater Pelecypoda the original free-swimming larval form has 

 undergone suppression, and in others a new form (such as the Glochidium of Unio) 

 has been acquired, in Dreissensia the larva is still a typical Trochophore. The 

 present part of Dr. Meisenheimer's memoir traces the ceil changes from the ovum 

 up to that important larval stage. 



The eggs are laid free in the water, where therefore the development takes place. 

 The segmentation is of the spiral type, and our author describes it very fully and 

 compares the stages with those described for Crcpidula by Conklin, and for the 

 Unioiiida; by Lillie. In addition to outline figures of the segmentation stages the 

 cell-lineage is illustrated by a folding plate representing the descent of each cell 

 graphically up to about the sixtieth generation of the blastomeres. These and the 

 other details given in the paper cannot be abstracted or understood a])art from the 

 figures, so we must refer those interested to Dr. Meisenheimer's paper itself for 

 further information. 



In conclusion, we welcome this paper not only for its own sake but also as 

 evidence of the good work now being done at the freshwater biological station of 

 Plon in Holstein, an institution of the kind that we certainly ought to have in 

 England before long, either on the Westmoreland Lakes or the Norfolk Broads, or 

 better still one in each of these interesting districts. — W. A. Hekdman. 



Appellor, A. — Cephalopodon von Ternate. I. Verzeichnis der von Professor 

 Kiikenthal gesammelten Arten. 2. Untersuchungen i.iber Idiosepius, Sepia- 

 darium und verwandte Formen, ein Beitrag zur Beleuchtung der Hektokoty- 

 lisation und ihrer systematischen Bedeutung. Abhandl. der Senckenberg. 

 Nat. Gesell., 1898, Bd. xxiv. pp. 561 — 637, Tfn. xxxii — xxxiv. 



This memoir opens with an enumeration of the Cephalopoda collected by Dr. 

 Kiikenthal ; no new forms are described, but three species {Octopus viticnsis, 

 Octopus 7)iollis, and Octopus pictus) are recorded for the first time from the Indo- 

 Malayan region. The second and much more important section contains an 

 elaborate discussion of the relationships of Scpiadarium and Idiosepius. The late 

 Professor Steenstrup maintained that the hectocotylisation, if rightly regarded, 

 might always be trusted to lead to a natural classification of the Cephalopoda ; and, 

 more especially, that those forms in which the modification affects the dorsal arm or 

 arms would always prove to be more nearly related to each other than to those in 

 which the modification affected the ventral pair. Now in the gener-a Idiosepius, 

 Scpiadarium, and Scpioloidca, the ventral pair is affected, and hence Steenstrup 

 united them with Srpia and Loligo rather than with SepioJa and Rossia, to which 

 they bear a strong external resemblance. The late Dr. Brock adduced grounds for 

 doubting this affinity in the case of Sejnoloidea, but Steenstrup replied to him, 

 maintaining his original thesis. Dr. Appellof has now in a masterly fashion rein- 

 vestigated the whole question. He finds that the peculiar rudimentary shell believed 

 to exist in Idiosepius was based on an error of observation; that a functional mantle- 

 connection is absent in all three genera, though present in a rudimentary form as in 



