SUMMARY OF CURRENT RESEARCHES RELATING TO 



Pycnogonids of the Faeroe Channel.*— P. P. C. Hoek describes the 

 Pycnogonids dredged by the ' Triton ' in 1882. Eleven species were 

 collected, one of which, Pallenopsis tritonis, is new. The cold-area 

 species found in the Atlantic occur also in the Arctic Ocean ; one 

 species, NympJion longitarse — does not appear to have its distribution 

 determined by the temperature of the water it inhabits. Within the 

 limits of the genus Pallenopsis there are species with three-jointed, 

 and others with two-jointed mandibles ; the former are of the more 

 ancient type, as is shown by their condition in Ascorhynchus and 

 Colossendeis, where, being larval or rudimentary, they have not been 

 strongly influenced by circumstances, and so retain their original 

 number. The original condition is seen in the deep-sea species, while 

 the shallow-water forms have two-jointed, and more robust, mandi- 

 bles. While NympJion stroemi has a number of small eggs, N. 

 macrum has a few in each egg-mass, and these are large. 



Development of Limulus.t— J. S. Kingsley begins his account after 

 the formation of the blastoderm. At this time there is a single layer 

 of cells surrounding the yolk, in which are scattered nuclei. The 

 mesoblast arises as a single sheet on the ventral surface. Its cells 

 come largely from the blastoderm, but some arise from the yolk 

 nuclei. The mesoblast soon forms two longitudinal layers, one on 

 each side in the neighbourhood of the limbs. The coelom is formed 

 by a splitting of the mesoblast, and at first consist of a series of 

 metameric cavities extending into the limbs. The supra-oesophageal 

 ganglion arises by an invagination of the epiblast. The heart arises 

 as two tubes in the somatophore, which later unite. The mesenteron 

 does not appear until after hatching. The amnion of Packard is the 

 first larval cuticle, and bears a resemblance to the amnion of the 

 Tracheata. A second cuticle is formed and moulted before hatching. 

 The eyes appear on the dorsal surface at the same time that the limbs 

 appear on the ventral. In these characters Limulus agrees essentially 

 with the Tracheata, and has nothing in common with Crustacea. 



S. Crustacea. 



Rate of Development of Carcinus maenas.l — Gr. Brook has for more 

 than two years been making observations on the rate of development 

 of the common shore-crab, and every cast shell has been carefully pre- 

 served and labelled. Only one ecdysis was observed to occur between 

 the end of October and the beginning of February, and the majority of 

 ecdyses happen in the summer months. It appears to be impossible 

 to judge the age of any particular specimen or the number of ecdyses 

 which it has passed through from a casual observation of it on the 

 sea-coast. Two given forms ("A " and " B ") might, two years after 

 hatching, be one 28 mm. long by 85 mm. broad, and the other 45 

 by 56 mm. Mr. Brook points out that it is probable that in con- 

 finement young Carcini do not develope with exactly the same rapidity 



* Trans. Eoy. Soc. Edinb., xxxii. (for 1882-3) pp. 1-10 (1 pi.). 



t Science Kecord, ii. (1884) pp. 249-51. 



i Ann. and Mag. Nat. Hist., xiv. (1884) pp. 202-7. 



