498 RECORD OF SCIENCE FOR 1886. 



into the posterior basal lobes of the cerebral ganglion." The arm nerves 

 aud brachial ganglion therefore owe their origin, " not to the pedal but to 

 the cerebral gauglioD,"aud von Ihering's suggestion that " the brachial 

 was really a separate portion of the cerebral gauglion," is thus cor- 

 roborated. 



The comparison is especially interesting between the structure of 

 Naiitil^is aud Sepia on the one hand and Dentalium on the other. The 

 body of Dentalium is so oriented that " of the two mantle apertures, the 

 larger, through which the foot projects, is turned forward and down- 

 ward, while the narrower lies at the apical pole of the body. The mantle 

 cavity occurs at the j)osterior side of the body." In connection with 

 the superior mantle aperture in Dentalium, considerable space is devoted 

 to the discussion of the origin and development of the mantle cavity 

 and cleft. Finally, it is contended that the arms of cephalopods are 

 homologous with and derived from the cirri of the scaphopod or denta- 

 lioid gasteropods, and special comparison is made with the tentacles of 

 Nautilus, each tentacle of the nautilus being regarded as homologous 

 with an arm of a dibranchiate cephalopoda These conclusions will 

 doubtless be dissented from by not a few morphologists. (Arbeit, zool. 

 Inst. Univ. Wien, vii, pp. 61-82 ; J. R. M. S. (2), vi, pp. 950, 951.) 



Living cephalopods. — The recent cephalopods have been investigated 

 by Mr. William Hoyle in connection with the specimens obtained by the 

 Challenger expedition, and a monograph of those acquired by the great 

 expedition, as well as " a catalogue of recent cephalopoda," has been 

 published. 



Mr. Hoyle admits, in his catalogue, " three hundred and eighty-eight 

 species, which are disposed in sixty-eight genera, and these into four- 

 teen families." Of these species at least sixty to seventy " have 

 been inadequately characterized, so that it is unlikely that they could 

 be recognized from the published descriptions, and the same is true of 

 several of the genera ; hence it may be said in round numbers that we 

 are acquainted with the fifty or sixty recent genera, containing three 

 hundred species. It is worthy of remarlv that twenty-nine, or half the 

 genera, contain only one species each, w^hile nearly one-half the species 

 one hundred and seventy, belong to the three genera Octopus, Sepia, 

 and Loligo.''^ 



The species have been considered by Hoyle with reference to their 

 distribution and have been referred to three primary groups: (1) the 

 pelagic; (2) the abyssal; and (3) the littoral. Those of the first two cat- 

 egories have been further associated together as "oceanic" species, and 

 have been distributed in three groups " corresponding to the Atlantic, 

 Pacific, and Indian (including the Southern) Oceans, rather from con- 

 venience than from a belief that such a division is natural, although 

 the great majority are confined to one area. The chief factor limiting 

 their spread," according to Mr. Hoyle, "is probably temperature, though 



