534 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The ovum is filled with yolk-spherules, among which are scattered 

 vesicular mitochondria or plastochondria. At the lower pole there is a 

 cupola-like accumulation of plastochondria, with an irregular surface, 

 with bays and prominences both externally and internally. The plasto- 

 somatic portion of the spermatozoon is traceable for some time in the 

 fertilized ovum. It probably represents a protoplasmic hereditary 

 material. Meves discusses various other possible interpretations of the 

 minute body, and defends his general position that the plastosomes are 

 of significance in inheritance. 



Regeneration and Budding in Diazona.* — M. Caullery describes 

 Diazona geayi sp.n., found by F. Geay on the coast of French Guiana — 

 a new region for the genus. He also discusses the remarkable retro- 

 gression which occurs in Diazona in unfavourable conditions, and the 

 subsequent regeneration. There is a degeneration of the thorax region 

 of the ascidiozooids and then repair. But the process may be complicated 

 by multiplication, the abdomen becoming fragmented into several pieces 

 in a line, each of which becomes a new ascidiozooid. The author dis- 

 cusses in particular what happens in regard to the digestive tube. 



INVERTEBBATA. 

 Molluaca. 

 7> Gastropoda. 



Structure of Trochidse.f — E. J. Frank has studied Monodonta 

 turbinata, Gibbula cineraria, and Photinula tseniata, to which we shall 

 refer by their initials. The shell consists of a periostracum, an ostracum 

 (3-layered in 67. c, 2-layered in M. t. and P. t.), and a hypostracum. 

 In P. t. there is no pigment in the skin, and there are no head-lobes as 

 in M. t. and 67. c. There is cross-striping in the muscles of heart and 

 pharynx. The left kidney (papillary sac) is probably a blood-gland ; 

 the other is a true kidney ; both have a reno-pericardial canal communi- 

 cating with the pericardium, but they do not communicate with one 

 another. The gonad opens into the right kidney, and the ureter func- 

 tions as a genital duct. There is a crop rich in villi ; the stomach has 

 a caecum ; the mid-gut gland has an absorptive as well as a secretory 

 function, and has two kinds of glandular cells. The nervous system is 

 carefully described. The pedal strands are elongated pedal ganglia, 

 and form a morphological and histological unity. They are connected 

 by cross commissures, and give off sole-nerves, lateral nerves, and 

 epipodial nerves. The anterior pedal nerves show no transverse com- 

 missure. The epipodium is innervated from the pedal strands and 

 the cerebro-pedal connectives, and is strictly part of the foot. The 

 statocyst nerve passes through the cortex of the pleural ganglia into the 

 cerebro-pleural connective, and probably belongs to the cerebral ganglion. 



* Bull. Soc. Zool. France, xxxix. (1914) pp. 204-11 (2 figs.). 



t Jen. Zeitschr. Naturw., li. (1914) pp. 377-486 (1 pi. and 55 figs.). 



