34 SUMMARY. OF CURRENT RESEARCHES RELATING TO 



easily influenced by certain factors of the environment. This labile 

 condition is nsually ascribed to the fact that the line is in about the middle 

 of the reproductive cycle, the diminishing tendency to parthenogenesis' 

 being about equally balanced by the increasing tendency to sexual re- 

 production. Such a balanced condition must, however, be passed 

 through, whether the tendency to sexuality is being increased by the 

 progress of the " cycle," or by the cumulative effect of an unfavourable 

 environment. Hence, the existence of labile periods is as readily ex- 

 plained on the one hypothesis as on the other. There is no justification 

 for retaining the hypothesis of an inherent reproductive cycle, that 

 is to say, the hypothesis that the number of generations or lapse of 

 time since the last fertilized egg influences, as such, the production of 

 sexual or degenerate forms. For the production of these forms 

 is under certain conditions not influenced even by the lapse of an 

 enormous number of parthenogenetic generations, while their production 

 certainly is influenced by environment in other cases. The residuum of 

 cases being equally well explicable on either hypothesis (cycle or en- 

 vironment) it is most reasonable to suppose that the factor that was 

 effective in the one case was the one that was effective in the other, and. 

 conversely, that the ineffective factor of the one case (" reproductive 

 cycle ") was ineffective in the other. 



Fresh-water Prawns from Tonkin.* — E. Sollaud describes Leander 

 mani sp. n. and Co ulierella tonhinensis g. etsp. n. The latter is one of 

 a number of small isolated fresh-water genera, such as Allocaris, Desmu- 

 caris, and Pseudopalsemon, oftenest with a single species, with large ova 

 and condensed development, and with a strange mixture of ancestral 

 and specialized characters. The structure of the maxilla in CoutiereUa 

 is very distinctive. In both types the eggs are large and relatively few, 

 and the development is condensed. The first larval form has all its 

 pereiopods and pleopods, and has even its uropods visible in a rudimen- 

 tary stage beneath the skin. 



New Barnacles. f — Nelson Annandale describes some new and 

 interesting pedunculate Cirripedes from Indian seas. The collection 

 includes Al&pas investigator is sp. n. with translucent tissues, white 

 except the yellowish cement glands, found like other members of the 

 genus on the umbrella of a pelagic medusa. Another new form, Heteru- 

 lepas (Parahpas) reticulata sp. n., is a very small animal, found on spines 

 of Cidarid sea-urchins. The external appearance is very distinctive ; 

 the capitulum is almost globular ; there is no carinal crest, but the 

 posterior part and the sides are covered with a reticulation of deep 

 grooves, and in the centre of each mesh there is a projecting tubercle. 

 Below the aperture the surface is smooth or marked with irregular 

 (mostly transverse) grooves. No scuta can be distinguished, but the 

 outline of a pair of irregular areas is sometimes indicated on the smooth 

 anterior part of the capitulum, in the position the scuta would occupy. 



* Bull. Soc. Zool. France, xxxix. (1914) pp. 314-24 (4 figs.). 

 t Records Indian Museum, x. (1914) pp. 273-320 (2 pis.). 



