640 SUMMARY OF CURRENT RESEARCHES RELATING TO 



sentative of a distinct family, the Arnphitretidse. This family probably 

 has its nearest ally in the genus Alloposus, the only essential distinctive 

 character being the presence of a ventro-median connection of the 

 mantle with the siphon in Amphitretus. Apart from Alloposus, which 

 Verrill made the representative of a special family Alloposidte, the 

 Amphitretidae seem more nearly related to the Octopodidas than to any 

 other of the eight-armed Dibranchiata. 



y. Gasteropoda. 



Blood of the Snail.* — E. Couvreur has made a physiological study 

 of the blood of Helix pomatia. It does not coagulate, which is difficult 

 to explain. Perhaps the globulin, which is precipitated by sulphate of 

 magnesium and is otherwise different from the fibrinogen of mammals, 

 is entirely combined with a cupriferous substance and incapable of be- 

 having like fibrinogen. 



The blood of this mollusc contains no glucose either during hiber- 

 nation or immediately afterwards. It contains a large proportion of 

 urea or of compounds of urea. The colouring matter (" hasmocyanin "), 

 which turns bluish on exposure to air, seems to be due to the combina- 

 tion of an albuminoid with a cupric substance, and is only remotely 

 analogous with haemoglobin. 



Tanganyika Gastropods : Chytra and Limnotrochus.t — Lettice 

 Digby discusses the structure and affinities of Chytra kirhii and Limno- 

 trochus thomsoni. The former shows an obvious combination of cha- 

 racters distinctive of several well-known Prosobranchiate forms, — 

 Capulus, Xenophorus, Aporrliais, Trochus, Pleurotomaria, Nassopsis, &c. 

 It is suggested that in Chytra we are probably dealing with the direct 

 ancestor of the families Hipponycidre and Capulidaa, since the genus 

 combines the nervous system of the one and the radula of the other, 

 i.e. two of the most salient features of Prosobranchiate structure. 



Like Chytra, Limnotrochus has scattered affinities, and it is more 

 difficult to place than even Chytra itself. It is undoubtedly allied both 

 to Chytra and to Typhobia, as well as to the Stromboid group repre- 

 sented by the genera Strombus and Aporrhais ; and it is perhaps more 

 nearly allied to these genera than to any other living types. But on 

 the other hand, it is quite distinct from them all, and must, at any rate 

 for the present, be regarded as unique. 



5. Liamellibranchiata. 



Artificial Parthenogenesis in Mactra.J — C. Kostanecki has made 

 numerous experiments with the ova of Mactra stultorum and M. helvacea, 

 which lead him to conclude that the beginnings of artificial partheno- 

 genetic development may be induced by increasing the concentration 

 of the sea-water or by adding various chlorides, &c. The unfertilised 

 ova under these conditions exhibited, but with considerable variability 

 of result, the protrusion of the polar bodies and a cleavage as far as 

 the 12-cell stage. It is possible, he thinks, that with more experience 



* Ann. Soo. Linn. Lyon, xlvii. (1901) pp. 85-91. 



t Journ. Linn. Soc. (Zool.), xxviii. pp. 434-42 (3 pis.). 



% Bull. Internat. Acad. Cracovie, 1902, pp. 363-87 (9 figs.). 



