December 14, 1883.] 



SCIENCE. 



773 



groove, if tlie latter is piesoiit. There appears to be a 

 widespread difficulty in comprehciiditig the concres- 

 cence of llie edges of the primitive month to form 

 the axis of the vertebrate body. — {Zool. anz., vi. o6.">. ) 

 c. s. M. [488 



Coelenterates. 



The life-history of American medusae. — .M- 

 though Turrito])sis is one of our most interesting 

 hydromedusae, its metamorphosis li.is been entirely 

 unknown. Brooks has added to McCrady's graphic 

 description of the adult an .account of the larva and 

 of the changes through which the young medusa 

 passes. The larva is very similar to Tubiclava All- 

 man; and the medusa buds are carried upon short 

 stems which grow out from the main stem, just be- 

 low the hydranth. When set tree, the medusa has 

 eight tentacles and a short simple probo.scis; but the 

 endoderm-cells of the radial canals soon become 

 thickened to form the great cellular peduncle, which 

 is the most characteristic mark of the genus. Adult 

 specimens of Turritopsis often contain the singular 

 Ounina larvae which were discovered in this situa- 

 tion by McCrady. 



Nemopsis liachci is another very common medusa, 

 tlie young stages of wliich have liitherto escaped ob- 

 servation. Brooks has reared it from a Bougauvilleia, 

 and has traced tlie metamorphosis of llie medusa. 



Phortis gibbosa McCr. has been reared from a very 

 singular canipanularian hydroid which was washed 

 jishore in great abundance at Fort Macon, on denuded 

 Aglaophenia stems. Only one medusa escapes at a 

 time, and this soon becomes larger than the entire 

 gonotheca. The order in which the tentacles appear 

 is shown in the following diagram. 



The larva of Amphinema apicatum Haeckel is a 

 Perigonomus, which grows upon the sand-tubes of 

 Sabellaria. When set free, the medusa has no trace of 

 the apical process, whicli is an adult feature, although 

 it has usually been regarded as a larval characteristic. 

 When five days old, the medusa begins to assume 

 the adult form : the apical process is developed, the 

 umbrella becomes like that of the adult, the oral folds 

 appear, and the upper end of the proboscis becomes 

 enlarged. — [Stud. hUA. lab. Jolinn Ilujik. uith-.. ii. 

 40.5.) AV. K. u. [489 



Moll asks. 



Extramarine moUusca of Nevsr Guinea. — Tap- 

 parone (Janefri has unilerlakcn a gencTal work on 

 the mollusta of New (iuinca, of which the first part 

 has just appeared in the shape of a fine octavo vol- 



ume of three hundred pages and eleven plates. In 

 proof-reading, typograpliy, and illustrations, it pre- 

 sents a marked and favorable contrast to many Italian 

 .scientific publications. The second volume will con- 

 tain the marine niollusks: the others find a place 

 liere. From such a region many novelties might be 

 expected. The author, however, is conservative ; and 

 the divisions newly proposed are not numerous, 

 though a considerable number of new species are de- 

 scribed, ami illustrated. Bcllardiella (Martensiana) 

 from Port Dorey is a Pupinella in which the peristo- 

 mal sulcus is replaced by a tube pi steriorly directed, 

 behind the lip. Sulcobasis and Crisiigibba are sec- 

 tions of Heli.\-, typified by H. snlcosa Pfr. and H. 

 torlilabia Less, respectively. Cyelotropis (papuana) 

 differs from Assiminea Ijy its perforated base. Phy- 

 sastra lesembles a thick-shelled reveised Limnaea 

 with a dehiscent epidermis. We doubt if it should 

 be referred to the Physidac. Lastly, the section 

 Microdontia is proposed as a section of Unionidae 

 for U. anodontaeformis, in which the anterior cardi- 

 nal teeth are thin, compressed, and Jicarly parallel 

 Willi the margin. 



Besides full descriptions or synonymy of species, the 

 work contains useful tables showing thh! exact distri- 

 bution of each species and group of species, as far as 

 known, and also dissections of the generative organs, 

 and ilhistrations of the dimtition of a number of spe- 

 cies. The work will also appear as volume six. of 

 the Annals of llie Musoo civioo of Genoa, and is pro- 

 vided Willi a ^iiod index. — w. ii. u. [490 



Structure of the oyster-shell. — Observations by 

 Osborne sliow that the shell is formed by the crys- 

 tallization of lime in the conchioline (not, as stated, 

 chitinous) layer, as is generally believed. The struc- 

 ture of other species was found less easy of inves- 

 tigation; and the complexity of structure in many 

 molluscan shells would indicate that the process of 

 formation is not universally the same. — {Slud. biot. 

 lab. Johns Uoplc. univ., ii. 4.) w. ii. d. [491 



Slime-spinning by Arion hortensis. — Mr. Roe- 

 back, having received a specimen an inch long, ob- 

 served it crawling on a flat paper-knife, from which 

 it projected in-a horizontal posiiion into the air. with 

 only the end of its tail touching the knife. Emit- 

 ting a thread of slime, it hung by it to a distance of 

 four inches; and when, on reaching a support, the 

 thread was severed, it inimcdialely shrank into a 

 niinute, scarcely visible point of slime. — (Journ. 

 con.c/i., July, 1SS3.J w. u. n. [492 



Insects. 

 Distribution of the Occident ant' — liev. Dr. H. 

 C. McCook made a comniunication on the geographi- 

 cal distribution of the Occident ant, I'ogonomyrmex 

 occidentalis. The specimens upon which the com- 

 munication was based were collected by Prof. J. E. 

 Todd in Dakota. lie reporls that the species is con- 

 fined to the bottom-lands along the Missouri River, 

 and has not pushed eastward through the territory. 

 This corresponds remarkably with Dr. McCook's con- 

 clusion, both from his own observations and those 

 made under his direction by Dr. Horace GrifiBth of 



