222 SUMMARY OF CURRENT RESEARCHES RELATING TO 



term prostate two organs have been confounded— the atrium of Pcrichieta, 

 Acanthoihihis, &c, and the atrium and prostate of Moniligaster. 



Histology of Pachydrilus enchytrseoides. *— For this marine Oligo- 

 chfflte, M. L. Roule finds it necessary to form a new genus, and he 

 proposes to call it Enchytrseoides Marioni. The ventral nerve-chain 

 exhibits a simplicity of histological structure which calls to mind the 

 arrangements in Archiannclids. There arc nerve-cells along its whole 

 length, and these are placed in the lower part of the band ; there are no 

 aggregations or thickenings which could be called ganglia ; the band is, 

 further, intimately connected with the ectoderm, not, indeed, along the 

 whole of its length, but at a number of points which appear to regularly 

 succeed ono another. The nephridia arc thick oval bodies, with a wide 

 vibratilo opening ; their interior is hollowed by a flexuous canal which 

 opens by a very small ventral pore ; this canal is hollowed out of the 

 cellular substanco itself. 



New Earthworm.t — Dr. W. B. Bcnham has a preliminary note on 

 a new earthworm, which is very interesting from the fact that it 

 possesses two pairs of nephridia in each somite. As it is very short in 

 proportion to its length it is provisionally called Brachydrilus. Tho 

 setEe are exceedingly minute. The spermathecoe differ in structure and 

 position from those of any other earthworm except Microchseta ; they 

 are small and oblong. This new worm has — like Lumbricus, but so 

 far as is known no other Oligochflete — capsulogenous, or, as Dr. Benham, 

 with Vejdovsky, prefers to call them, albumen-glands ; their lumen is 

 lined with short columnar cells which are surrounded by a layer of 

 muscles, and outside these are the large glandular cells with very 

 granular contents. Each nephridium corresponds in position to one of 

 the couples of setae, and those of each side are quite separate from one 

 another ; the organ somewhat resembles that of Lumbricus, but the tube 

 is much less coiled. Dr. Benham inclines to the view that the nephri- 

 dia of Oligochretes were primitively, as they are still in many species of 

 Perichseta, numerous scattered tufts of tubules ; with suppression of 

 some there has been increase in size of others, and some in certain 

 somites have taken on the function of genital ducts. 



Organization of Annelids.^ — Herr E. Meyer has an elaborate 

 memoir on the organization of Annelids. He commences with an 

 account of the nephridial system of the Terebelloidea — a name formed 

 for a group containing the Terebellacea, Ampharetea, and Amphictenea. 

 This group is remarkable for the internal division of the anterior body 

 region, which is ordinarily known as the thorax, into two unequal 

 chambers, each of which consists of a number of segments. These two 

 divisions are separated from one another by a strong muscular dia- 

 phragm. The anterior is the smaller, and contains, as a rule, only the 

 head and the gill-bearing segments; the hinder one is always much 

 larger and is often continued into the abdomen. In both, the ordinary 

 dissepiments are completely wanting. In most cases the septa in the 

 abdominal region are broken through at definite points, so that all the 

 segmented chambers of the abdomen communicate not only with one 

 another, but also with the post-diaphragmal space of the forebody. The 



* Comptes Itendus, cvi. (1888) pp. 308-10. t Zool. Anzeig. xi. (1888) pp. 72-5. 

 % MT. Zool Stat. Neapcl, vii. (1887) pp. 592-741 (G pis.). 



