ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 531 



Annulata. 



Studies on Oligochaeta.* — Asger Ditlevsen discusses the systematic 

 relations of the Oligochaata, and has made a special study of the sexual 

 reproduction. 



He begins with an investigation of the Naidse, and of the genus 

 Ilyodrilus Stole in particular, of which two new species are established. 

 A grouping of the forms of Tubificidaa is submitted, with descriptions 

 of two new species of Psammoryctes, one of Tubifex, two of Monopele- 

 phorus. The Enchytra^idas are then dealt with, and this section includes 

 descriptions of a new species of Pachydrilus, and a new species of 

 Mesenchytmus. 



The next section is devoted to the advent and duration of the sexual 

 period in Tubificidaa, Naidaa, CliEetogastridas, iEolosornatida?, and Lum- 

 briculidse. Then the author passes to the copulatory phenomena in 

 Enchytraaidaa, Naidse, Chaetogastridas, and Tubificidaa, in regard to 

 which he has much that is new to say. In Enchytraaidaj, Naidas, Chaato- 

 gastridaa, Lumbriculidge, and Tubificidae, the clitellum functions solely 

 as a cocoon-forming structure, while in Lumbricidas it has also to do 

 with copulation. The oviposition in the different families is then 

 discussed. 



Priapulidae of Scandinavia.f — M. Herubel gives some notes on 

 the geographical distribution and comparative anatomy of the Pria- 

 pulidaa of the west side of Scandinavia. He found their distribution 

 very local. There appear to be four conditions requisite — shallow 

 water with mud or sand and mud, absence of strong currents, low but 

 variable temperature, and nearly constant salinity. He distinguished 

 three distinct varieties of P. caudatus. In the first there is a medium- 

 sized ring of denser tissue, and uniform appearance, between the intro- 

 vert and the body ; a second form has this ring very large, and in the 

 third it is absent. These differences, which are accompanied by other 

 anatomical peculiarities, were made out upon living specimens. The 

 varieties are from separate localities. A second paper discusses the 

 integumentary characters. 



Digestive System of Hirudinea.J — Canaille Spiess compares the 

 alimentary tracts of Hirudo medicinalis and Aulastomum gulo, and em- 

 phasises the detailed differences between a species living on blood and 

 a species living on worms and molluscs in a voracious carnivorous 

 fashion. The differences are striking, ar.d illustrate, according to the 

 author, "the modifications which the digestive apparatus may exhibit 

 under the influence of different nutritive regime." They illustrate, at 

 any rate, different adaptations to different diet. 



Nematohelminthes. 



Differences in the Chromosomes of Sister-germ-cells.§ — Th. 

 Boveri recalls the fact that in the development of Ascarids, the chromo- 



* Zeitschr. "wiss. Zool. Ixxvii. (1904) pp. 398-480 (3 pis.). 

 t Bull. Soc. Zool. France, xxix. (1904) pp. 100-9, 126-9. 

 X C'omptes Rendus, exxxviii. (1904) pp. 1123-4. 

 § SB. Phys. Med. Ges. Wiirzburg (1904) pp. 16-20. 



