96 Chaetognatlii, Crustacea. 



Botli species were found living as commensals on Polychaet worms belonging 

 to the family Maldanidae from the west coast of Scotland. The specific name of 

 L. saltans indicates its habit of locomotion by jumping. In this action four of 

 the tentacles, which are longer than the others and are moved separately, take 

 part. In L. saltans too the alimentary canal is differentiated more markedly into 

 glandulär, absorptive and excretory regions than in L. loxalina and the glandulär 

 diverticula in particular are highly developed. The excretory organs are a pair 

 of lophophoral and a pair of body kidneys, both being large vacuolated cells. 

 A pair of ducts is probably associated with the lophophore organs but they are 

 not ciliated. There is no evidence of the existence of soleuocytes in the living 

 animal. Potts (Cambridge). 



281) Pixell, H. L. M., Two new species of the Phoronidea from Vancouver 

 Island. In: Quart. Journ. Micr. Sei., Vol. 58, S. 257— 284, 16 Textfig., December 1912. 



Chaetognathi. 



282) Michael, E, L. (California, Scripps Institution), Vertical distribution 

 of the Chaetognatha of the San Diego region in relation to the 

 question of isolation vs. coincidence. In: Amer. Nat., Bd. 47, Heft 1, 

 S. 17 — 49, 1913. 



A study was made of the vertical distribution of the Chaetognatha in the 

 sea-water of the San Diego region, California. This included 18 species of Sa- 

 gitta and certain species belonging to other genera. The plancton hauls yielded 

 in all nearly 70000 specimens, and it was found that the vertical distribution 

 brings together forms which are unlike in morphological characters. Thus as 

 regards characters there are five "couplets" of species of Sagitta, but with one 

 exception only one of each couplet occurs iu the San Diego region. Each species 

 was found to have a definite and specific vertical distribution. It was further 

 found that the most diverse species have the most coincident distribution, and 

 that at a given depth nearly all the mature forms belong to one species. Thus 

 there may be coincident distribution as regards latitude and longitude, yet com- 

 plete isolation as regards vertical distribution. The vertical distribution is found 

 to be as truly specific as the morphological characters. This distribution, it is 

 pointed out, is the exact reverse of that which would be expected if the species 

 are gradually differentiated by natural selection. Gates (London). 



Crustacea. 



283) (xrosTenor, G. H. (the late) and Geoifrey Smith (Oxford), The Life- 

 Cycle of Moina rectirostris. In: Quart. Journ. Micr. Sei. (London), Bd. 58, 

 S. 511, 1913. 



The authors have tested Weismann's statement that the Cladoceran life- 

 cycle was fixed and independent of external conditions. Using Moina as the sub- 

 ject of the experiments this was found to be not the case. It was shown by iso- 

 lating parthenogenetic females at birth and maintaining them at a temperature 

 of from 25" — 35° C, that no males were produced in the brood: if, however, the 

 parthenogenetic females were crowded together at the same temperature males 

 appeared to the number of 307o while a lower temperature of 14° C gave 52 % 



