38 Echinoderma. 



Murex ramosus. Experiment showed that the species with large processes have a 

 liigh relative immunity compared with those Avithout processes, wlien kept in 

 similar environment, and that the species without processes can only live in an 

 environment in which they are protected from the attacks of the Murex. 



Doncaster (Cambridge). 



81) Lindsay, B. (St. Andrews University). On the boring Mollusca of St. An- 

 drews. In: Ann. Mag. Nat. Hist. 9, 51, S. 369-374; 1912. 



Gives evidence that the rock-boring of Pholadidae is performed mechanically and 

 is not assisted bv an acid secretion. Doncaster (Cambridge). 



82) Stafiford, J., Supplementary observations ou the development of the 

 Canadian oyster. In: Amer. Nat. 46, 29—40, 1912. 



It is shown that the larva of the oyster (Ostrea virginica Gmel.) continues in the 

 free-swimming condition ibr 3 or 4 weeks after fertilizatiou, the method used being to 

 collect the larvae from sea-water in a plancton net. It is thought possible to apply 

 this method in determining the time when the larvae settle and become attached, and by 

 supplying a suitable resting place on the sea bottom at the proper time, to enable a 

 much greater percentage of the larvae to survive. Various other data regarding the oysters 

 of the Atlantic and Pacific coasts are given. Gates (London). 



Hierzu: Nr. 42, 43, 49. 



Echinoderma. 



83) Mac Bride, E. W. (London, Imperial College of Science), Studies in 

 Heredity I. The Effects of Crossing the Sea-urchins EcJiinus esculen- 

 tus and Eclnnocardium cordatum. In: Proc. Royal Society, 84. Bd., 573. Heft, 

 S. 394—403. 



The results obtained by previous investigators are reviewed and a description 

 given of the normal larvae of the two species used. Echinocardinm is characterised 

 chiefly by an aboral spike and lattice-skeleton in the post-oral (anal) arms, EcJiinus 

 by the absence of both these characters, by differences in the body-rods, in size 

 and pigmentation. In the cross Eclnnocardium $ x EcJiinus c? only about one in 

 1000 fertilised eggs develop into larvae. The plutei are distinctly intermediate 

 between those of the two parents, having (with one exception) no trace of aboral 

 spike, imperfect lattice-work in the post-oral arm skeleton, body rods resembling 

 those of Echinus, but size and pigmentation nearer those of the maternal parent. 

 These results are at variance with those obtained by Vernon. No larvae could be 

 obtained from the converse cross; it was found however that unless the sea-water 

 was thoroughly sterilised, the eggs developed owing to the presence of EcJiinus 

 sperm in the water. Doncaster (Cambridge). 



84) Milies, G. ß. (Cambridge University), Note on the Mechanism of 

 Discharge of the Cuvierian Organs of Holothuria nigra. In: Quart. 

 Journ. Micr. Sc. 57. 3. S. 301— 304. 1 plate. 1912. 



It has' been maintained that the discharge of the Cuvierian organs is not 

 due to injection of fluid into the tubes, since if they are cut off during discharge 

 the separated pieces continue to elongate. The author made a variety of experi- 

 ments such as ligaturing the organs during discharge and injecting them with 

 water of known pressure, and proves that injection of fluid by muscular con- 

 traction of the body-wall of the animal is the cause of the discharge. The rea- 

 son for the continued elongation after section is that cutting with scissors causes 



