314 SUMMARY OF CURRENT RESEARCHES RELATING TO 



completed in the first day, and seems to be holoblastic. Tlie egg 

 hatches as an early Yeliger larva, which has a prolonged free-swimming 

 life, passing through a late Veliger stage before the adult form is 

 reached. In L. obtusata the capsules are aggregated in masses, and 

 attached to weeds ; the egg hatches as a fully-formed Veliger, and the 

 free-swimming period is thus much abbreviated. The chief food of 

 L. littorea appears to be the hairs of Fiirvs and allied seaweeds ; Blegvad 

 says it eats also animal detritus. The characteristic climbing habit has 

 not to do with nutrition ; it is dependent on the calmness of the sea. 



J. A. T. 



Breeding of Cerions.— Paul Bartsch {Dept. Mar. Biol. Carnegie 

 Inst. Washington, 1920, 14, 1-55, 59 pis.). Numerous colonies of these 

 land-snails, each with an individuality of features, occur on the Bahamas. 

 They are nocturnal in habit, feeding on fungi, and though hermaphrodite 

 do not reciprocally fertilize one another. A number of forms were 

 transported to the Florida Keys, where there is a considerable variety of 

 climate and vegetation. There is a native species, Cerion incanum 

 (Binney), but it is very remote from any of the forms introduced. One 

 of the interesting results obtained was crossing between G. incanym and 

 the very different C. viaregia. There resulted a complex of forms in a 

 state of flux. Had this been described by a naturalist not aware of the 

 history it would have been described as an instance of a very variable 

 species. But its heterogeneity was tlie result of the outbreeding. The 

 inference is that similar heterogeneous colonies may be the result of 

 outbreeding. The crossing is spoken of as having an energizing effect 

 on the new product, but this may be the result, one would think, of the 

 pooling of corroborative hereditary characters rather than of a physio- 

 logical stimulus in the hybrid offspring. Many of the Bahama colonies 

 illustrate the homogeneity which follows the inbreeding consequent on 

 isolation or insolation. J. x\. T. 



S, Lamellibrancliiata. 



Crystalline Style in Mya arenaria.— Charles Howard Edmoxdson 

 {Journ. Exper. ZooL, 1920, 30, 259-91, 30 figs.). About 50 p.c. of 

 individuals survive the extraction of the crystalline style by a severance 

 of the style sac. A new style is formed in the proximal portion of the 

 style sac in about 74 days when the conditions are most favourable. It 

 is seen beginning at the end of the fourth day as a dehcate sheath 

 of mucus enclosing a core of food material, and lies on one of tne 

 typhlosoles, usually the right. It grows more rapidly in sununer than 

 in winter. Under favourable conditions a crystalline style is reformed 

 in the short distal portion of the style sac, whicii is entirely separated 

 from the proximal division by the operation. This proves that the 

 epithelium of the style sac is the source of the crystalline style. The 

 axillary food core disappears as the style becomes fully formed. The 

 ingestion and digestion of food is apparently dependent upon the degree 

 of develoinnent of the crystalline style, since not until the organ reaches 

 a state of sufficient maturity to be projected into the stomach does the 

 ingestion of food occur. The animal may be kept alive out of water 



