SUMMARY OF CURRENT RESEARCHES RELATING TO 



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more independent of one another; the gland is much larger, and 

 occupies nearly the whole of the space between the digestive tube and 

 the walls of the body ; the tube being bent on itself, gives rise to the 

 appearance of two tubes imbedded in the gland, when this is cut 

 through. The addition of a little chromic acid reveals the ciliated 

 funnel. After a careful consideration of all the facts, Prof. Perrier 

 comes to the conclusion that in many Oligochseta and perhaps in all, 

 in the Hirudinefe, the Mollusca, and the Vertebrata, the vibratile 

 infundibula of the segmental organs are always altogether independent 

 of the generative apparatus, and form an integral part of the excretory 

 system. It is true that in the Brachiopoda and the Gephyrea un- 

 doubted segmental organs take part in the service of the genital 

 organs ; but it is the entire organ which forms the duct, and not the 

 infundibulum only ; in other words, the author does not agree with the 

 theory of Cosmovici. 



The testicles are placed in the eleventh and twelfth segments, and 

 the ovaries in the thirteenth. The former are large whitish glands, 

 occupying nearly the whole of the segment, when mature. The author 

 cannot accept the view of Kay Lankester that there are two pairs of 

 segmental organs typically in each segment, one of which may become 

 modified to form a part of the generative apparatus. 



The circulatory system does not possess the sub-neural vessel, 

 which appears to be found in all other terricolous Oligochteta ; the 

 system is very complicated in the anterior end of the body, where 

 there are no less than five longitudinal vessels ; the intestinal hearts 

 have a double communication with the two dorsal vessels, an arrange- 

 ment which, though not peculiar to Pontodrilus, seems only to be 

 found also in a new species of Titanus — T. forgiiesi. 



The dorsal pores, by means of which the body-cavity of Lum- 

 hricus is put into communication with the exterior, seem to be wanting 

 in Pontodrilus, as in Urochceta ; the most striking peculiarities in the 

 enteric canal are the absence of the muscular gizzard, and of the 

 typhlosole, the place of which seems to be occupied by a dorso- 

 intestinal vessel. 



In these last two points, as in the absence of the sub-neural vessel, 

 the position of the male generative orifices, the simplicity of its loco- 

 motor setae, as well as in the relative complexity of the vascular appa- 

 ratus, and the small size and mode of development of its ova, Pontodrilus 

 resembles the Naidina ; in others, however, it is just as clearly a ter- 

 ricolous Lumbricid, and it conclusively shows that too great a dis- 

 tinction has been made between these two divisions of the Oligochaeta. 



Action of Worms in the Formation of Vegetable Mould.* — 

 Mr. Darwin here details the results of a series of observations on the 

 share which earthworms have taken in the formation of the layer of 

 vegetable mould which covers the whole surface of the land in every 

 moderately humid country, prefaced by an account of their structui-e 

 and habits. 



* Darwin, C, ' The Formation of Vegetable Mould through the Action of 

 Worms, with Observations on their Habits.' 326 pp. (15 figs.) (8vo, London, 

 1881.) 



