ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 647 



the archoplasm (yolk-nucleus) is a specific substance, but the authors 

 were not able to come to any decision as to its origin, whether cyto- 

 plasmic or nuclear. 



Regeneration of the Nervous System of Lumbricidae.* — H. W. 

 Rand has made a very detailed study of this, with especial reference to 

 the centrosome of the nerve-cells. There is usually present in the nerve- 

 cells of Lumbricidae a centred system, consisting of centrosome and 

 radiations. A centred system like that found in nerve-cells of normal 

 worms is found in the regenerated nerve-cells ; and its chief centre, or 

 centrosome, is the centrosome of the last mitosis in the history of the 

 cell. That the function of this centred system is mechanical seems 

 very probable. The author also describes the occurrence of centrosome 

 and radiations in some resting cells of recently regenerated epidermis ; 

 and gives a full account of the minute structure of the nerve-cells both 

 n >rmal and regenerated. 



Habits of Earthworms. f — Dr. K. Bretscher brings forward evidence 

 to show (1) that earthworms normally shift about from place to place to 

 secure food and mates ; (2) that there is no definite relation between the 

 burrowing and burying operations and the form of the body in different 

 kinds ; and (3) that there is still much need for precise observations on 

 the processes of reproduction, e.g. as to the mucous bonds during copu- 

 lation which are sometimes present and sometimes absent. 



Incomplete Duplication of Parts in Nereis virens4 — C. W. Prentiss 

 describes a case of incomplete duplication of parts and apparent " regu- 

 lation " in Nereis vireiis Sars, the specimen being a sexually mature male. 

 From his study of this interesting case, he concludes (1) that a single 

 metamere of a Polychsetc may give rise to a complete or partial duplica- 

 tion of the main axis of the body : (2) that the production of such 

 abnormalities is in all probability due to traumatic stimulus in a post- 

 embryonic stage ; and (3) that the supernumerary, and in some cases 

 useless, parts thus formed may be gradually suppressed by regulative 

 changes which take place in the formative segment and tend to restore 

 it to the normal. 



Cocoon of Hirudo.§ — B. Sukatschoff returns to this subject, and 

 points out that the substance of the cocoon is certainly not chitin, that 

 it consists of an albuminoid, very probably near allied to keratin. 



Nematohelminthes. 



Method of Infection with TJncinaria duodenalis. |j — Dr. A. Looss 

 has been able to prove in a most satisfactory way that this parasite is 

 capable of reaching the alimentary canal in the human subject by 

 active movements through the skin, no less than by passive infection 

 through the mouth. His suspicions were first aroused by finding that, 

 after some months' work with ripe larvos, he himself was strongly 



I* Bull. Mus. Harvard, xxxvii. (1901) pp. 85-164 (8 pis.), 

 t Biol. Centralbl., xxi. (1901) pp. 538-50 (3 figs.), 

 j Anier. Nut., xxxv. (1901) pp. 563-74 (6 fiers.). 



§ Zool. Anzeig., xsiv. (1901) pp. 604-S. Of. this Journal, 1899, p. 578. 

 |1 Centralbl. Bakt, 1" Abt., xxix. (1901) pp. 733-9 (1 pi.). 



2x2 



