404 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Annulata. 



Spermatophores of Earthworms.* — F. E. Beddard describes the 

 structure of the spermatophores in earthworms of the genus Pheretima 

 (= Perichseta). They are like long-stalked pears, and as many as seven 

 were found in one spermatheca. It seems probable that the spermatozoa 

 are liberated by phagocytosis of the walls of the spermatophores. Within 

 the case of the spermatophore there is a delicate case around the sper- 

 matozoa. The latter are arranged in a quite definite way, with the heads 

 all on that side of the sperm mass which is nearest to the " stalk " of the 

 spermatophore. In addition to the spermatozoa the spermatophore con- 

 tains a granular mass which fills up the available space above the delicate 

 case containing the spermatozoa. 



Structure of Branchiomaldane vincenti.f — J. H. Ashworth gives an 

 account of this tubicolous Polychffite, and shows that it is more closely 

 related to Arenicola than to any other Pulycha^te. It presents some 

 primitive characters, such as a simple conical prostomium and homo- 

 nomy of its segments, but it affords considerable evidence of having 

 undergone secondary modification and retrogression. Its small size, tlie 

 simple form of its gills, the absence or great reduction of certain sense- 

 organs (statocysts and nuchal organ), the reduction in the number of 

 nephridia, the hermaphroditism, the large size of the egg and the absence 

 of a free-swimming larval stage — features in which Branchiomahlane de- 

 parts from Areiikola — are probably correlated, to a large extent, with 

 the much more sedentary life of the former. 



Nematohelminthes. 



Sex-chromosomes in Ascaris felis.|— C. L. Edwards finds in the 

 nuclei of the first spermatocytes of Ascaris f el is, shortly Ijefore the divi- 

 sion, eight bivalent autosomes and one pair of unequal chromosomes, 

 conspicuous in size and comparable to the x- and ^-chromosomes de- 

 scribed in Hemiptera. At a later stage there are spermatids with 

 ^^-chromosomes and spermatids with y-chromosomes. The author agrees 

 with those who regard these as sex-chromosomes — as constituting a link, 

 probably an essential one, in a chain of factors by which sex is determined 

 and inherited. 



Platyhelminthes. 



Structure of Cestodes.§ — Hans Zerny describes the minute structure 

 of Rhynchohothrius tetrabothrius v. Benedeu with particular reference to 

 the head (with its four suckers and fourfold proboscis), the male g<nital 

 apparatus (where the place of a cirrus-pouch is taken by a " cirro-motion 

 bladder " — a secretory, muscular evagination of the vas deferens or penis 

 sheabh), and the female genital apparatus (with a union of yolk-ducts 

 into a single duct, with a preformed uterus-opening and other peculiarities). 



• Proc. Zool. Soc. London (1911) pp. 412-20 (3 figs.). 



t Proc. R. Soc. Edinburgh, xxxii. (1912) pp. 62-72 (1 pi.). 



t Arch. f. Zellforsch , vii. (1911)pp. 309-13 (1 pL). 



§ Arbeit. Zool. Inst. Univ. Wien, xix. (1911) np. 297-316 (1 pi. and 6 figs.). 



