422 . NATURAL SCIENCE. Dec, 



The form and variations in their distribution are described in 

 detail by the author. The first segment in all cases is without 

 bristles. In the Geoscolicidae they are wanting in several of the 

 more anterior segments ; in Kynotus, for example, there are twenty 

 segments without bristles. A " cephalisation " is caused, partly 

 through this lack of bristles, partly through the absence of 

 dissepiments in two or three of the front segments, and through the 

 development of countless muscles in the peripharyngeal body-cavity. 

 Even the nephridia are deficient or modified in this respect. 



Referring to the epidermis, the author cites the well-known 

 relationships of the higher families, and, as in the case of the structure 

 of the clitellum, he refers by name to the works of Claparede, 

 Horst, Mojsisovics, and Cerfontaine, while the communications of the 

 reviewer are not mentioned. Special elements of the epidermis are 

 modified into the sense-cells, particularly in the prostomium ^ ; in Slavina 

 the sensory elevations are present on each segment. Further, the 

 goblet-shaped organs of the Lumbricidse, and the sense-girdle in 

 Rhynchelmis are described. Also the large gland-like cells in the 

 hypodermis of Pontoscolex and Onychocheta are held by Beddard 

 to be sense-cells. Finally, Beddard and Horst describe in Eiidvilns 

 oval bodies in the epidermis in connection with nerves, and compare 

 them to the corpuscles of Pacini. 



With regard to the structure of the muscles and their development, 

 the author refers to the works of Cerfontaine and of the reviewer. 



The nsrve-system shows very primitive relationships only in 

 Aeolosoma, while in the rest of the Oligochseta independent cerebral 

 ganglia and a ventral cord are present. The former lie in the first 

 segment in the lower forms, and in the fourth in the higher, where they 

 are at the same time proportionately smaller than in the lower 

 species. The peripheral nerves of the brain are present in varying 

 number ; in the Lumbricidee, as Pisarovic has recently shown, in one 

 or two pairs. Usually it is said that three pairs of nerves proceed 

 from the ventral cord, but according to the data of the last-named 

 author, there are in the hinder segments of Allolobophora fcetida only 

 two pairs, the hinder one of which (praeseptal, corresponding to the 

 double nerve-segment) stands in a very interesting relationship to the 

 dissepiment and nephridium ( = septonephridial nerve). The visceral 

 nerve-system of the Lumbricidse is so far not known, but in Megascolides 

 Spencer, 2 and Poutodvilus Perrier, it has been shown. One can feel 

 most secure about this part of the nerve-system in Chcslogaster, and 

 in the Enchytraeidae, as I have elsewhere shown. The lateral 

 ganglion-cell strings of the lower Oligochaeta have lately been 

 declared by Hesse to be unmodified parts of the so-called "nematoid" 

 muscle-fibre. The histological structure of the nerve-system is repre- 

 sented according to the data of Retzius, Friedlander, and the reviewer, 

 and its development according to Wilson, Bergh, and the reviewer. 

 The lymphoid corpuscles of the body-cavity are thought to be 

 phagocytes. 3 In the coelom of some Oligochaeta special sacs have been 

 discovered, in which the vascular system is enclosed. Beddard calls 

 them " perihaemal spaces," and mentions such in Deinodrilus, where 



1 Compare the interesting essay on this matter by Fanny Langdon, Jonni. 

 Moi'ph., 1895. 



2 From my own personal researches I can confirm Spencer's data. 



3 Compare the recent communication of Lim Boon Keng " On the Coelomic Fluid 

 oi Lumbriciis teri-estris in Reference to a Protective Mechanism." Phil. Trans. Roy. 

 Soc. London, v., 186 (1895), PP- 383-399- 



