216 SUMMARY OF CUIIRENT RESEARCHES RELATING TO 



Early Development of Loligo.* — The segmentation of the egg and the 

 formation of the germinal layers of Loligo Pealii are described by Mr. 

 A. T. Bruce. 



The protoplasm of the egg segregates to one pole, forming a germinal 

 disc, which is segmented throughout its thickness. It then becomes split 

 into two layers of cells, the ectoderm and mesoderm ; but along a line, the 

 future long axis of the embryo, the ectoderm alone is present, and in the 

 region of this line certain cells separate from the mesoderm, which from 

 the spindle shape and oval nuclei are recognized as endoderm cells. As 

 no nuclei were observed in the yolk, no endoderm cells are derived there- 

 from spontaneously. The mesoderm bands become two cells thick ; the 

 endoderm spreads, and soon the ectoderm and endoderm surround the whole 

 yolk, whilst the mesoderm extends only half-way round. A slight pro- 

 minence in the centre of the embryonic area is the first trace of the mantle, 

 and at this stage the two mesoderm bands were no longer separated. 



' Challenger ' Cephalopoda.t — Mr. W. E. Hoyle's report on the Cephalo- 

 poda collected by the ' Challenger ' is almost completely systematic in 

 scoj)e ; when careful attention was given to the characters of the radula, 

 whence it was hoped assistance might be derived which would be important 

 in the limitation of the sj)ecies, it was found " that in almost every radula 

 each row of teeth diifers a little from the one jireceding it, and very 

 frequently five, six, or even more rows must be examined before a given 

 form rejieats itself; two rows of teeth from the same specimen will often 

 differ as much as two from different species." From this it follows that 

 the majority of figures hitherto published of Cephalopod radulse are quite 

 useless for diagnostic purposes. 



A new family of Amphitretidse is formed for Amphitretus pelagicus, 

 which is unique among Cephalopods in having the mantle fused with the 

 siphon in the median line, so that there are two openings into the branchial 

 cavity, one on either side. Japetella is remarkable for its gelatinous semi- 

 transparent body, but, unfortunately, like a number of other ' Challenger ' 

 specimens brought up by the trawl, there is considerable uncertainty as to 

 its real place of origin. Promaclioteutliis is provisionally defined, as only 

 one specimen of a single species is as yet known. A special report on 

 Spirala is being prepared by Professor Huxley ; ten new types are added to 

 the genus Sepna. From the stomach of a shark there were taken fragments 

 of a gladius, which, if correctly referred to the genus Chiroteuthis, indicates 

 that that genus must attain to dimensions hitherto unsuspected ; what can 

 be pieced together of this fragmentary pen amounts to 78 cm. Histiopsis 

 is a new type, intermediate between Callifeuthis and Histioteuthis. The 

 remarkable larva described by Eay Lankester as Procalistes Suhmii is 

 referred to the genus Taonius. 



Very few pelagic Cephalopods were obtained by the ' Challenger ' ; this 

 may be explained by the enormous activity of these animals, which can only 

 be captured when the vessel is going at great speed, or when, in other 

 words, it is difficult or impossible to use a tow-net ; the investigation of 

 the contents of the digestive tracts of predaceous birds, fishes, and Cetacea, 

 will probably do much to increase our knowledge of these molluscs. Apart 

 from the fact that Batliyteuthis and MastigoteutJds have slender filiform 

 tentacles with minute suckers, no structural features have been discovered, 

 which will serve to distinguish a deep-sea form from a shallow-water one. 



* Johns-Hopkins Univ. Circulars, vi. (188G) pp. 45-6. 



t Report of tlu; Voyage of H.M.S. ' Cliallengtr,' Monograph xliv., 4to, London, 

 188G, 245 pp. and 37 pis. 



