200 SUMMARY OF CURRENT KKSEARCHES RELATING TO 



Echinoderma. 



Fertilization and Phagocytosis,*— Jacqiies Loeb suggests that the 

 absorption of the spermatozoon by the ovum may be regarded as a kind 

 of phagocytosis. He bases his suggestion on a study of the conditions 

 which make it possible to fertilize the ova of a sea-urchin, Strongy- 

 locmtrotus purpuratus, with the spermatozoa of a starfish, Asterias 

 ochracea. It is not proved that the entrance of the spermatazoon into 

 the ovum depends on processes of phagocytosis (or surface-tension), but 

 the idea of phagocytosis facilitates the interpretation of the phenomena 

 which condition penetration. 



Coelentera. 



Studies on Living Corals.t — T. W. Vaughan distinguishes two 

 sub-faunas in the West Indies coral reef : (1) the strong, firmly-attached, 

 usually massive forms, which can withstand breakers and the pounding 

 of the surf, e.g. Orbicella annularis and Acropora palmata ; and (2) the 

 weakly-attached and branching forms, which can only survive in quiet 

 water, e.g. Maeandra areolata and Porites furcata. 



The depth to which the more massive forms extend is between 

 18 and 31 metres ; in general, the lower depth of the shoal- water 

 coral fauna of the West Indies is about 37 metres, approximating to 

 conditions in the Pacific. 



All the corals studied have the capacity of removing sediment from 

 their surfaces. This is effected by the non-nutrient particles becoming 

 imbedded in mucus, and by cilia wafting off both. 



The food-catching depends on ectodermic nematocysts, ectodermic 

 cilia, mucus secretion, tentacular action, and mesenteric filaments, which 

 in many species can be extruded through the column walls. The food 

 is purely animal plankton. 



Strong light is essential for the vigorous growth of shoal-water corals. 

 The minimum temperature for viability is about 18' 15° C. Reef -corals 

 are usually, if not always, confined by temperature to water less than 

 18u metres deep. The limiting of downward growth is also affected by 

 sediment, illumination, and food supply. The saHnity limits are between 

 27 and 38 p.c. 



The larval forms are able to swim for two to twenty-three days, which 

 explains the wide distribution. The growth of Orbicella annularis is from 

 5-7 mm. per year. Any known living coral-reef might have formed 

 since the disappearance of the last continental ice-sheets. 



Physiology of Medusae. J — Naohide Yatsu has made interesting 

 observations on Charyhdea rastonii, a Cubomedusa common at Misaki. 

 Transference from diffused light to direct sunlight evokes no change in 

 the swimming. The concretion is always at the lowest end of the 

 rhopalium, whatever be the position of the animal. Extraction of the 

 concretion does not cause any change in swimming. Medusre deprived 



* Ann. Inst. Pasteur, xxxi. (1917) pp. 437-41. 



t Proc. Nat. Acad. Sci. U.S.A., ii. (1916) pp. 95-100. 



1 Journ. Coll. Sci. Univ. Tokyo, xl. (1917) pp. 1-11 (5 figs.). 



