EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 169 



GOPPERT. Uebersicht der arbeiten, &c., der schlesischen gesellschaft 

 &c. fur 1840, Breslau 1841, " On the structure of Piso- 

 lithus arenarius." 



KORBER. Id. p. 95, 99, " Upon the relation of the Gonidia with 

 the Soredia of lichens." 



[From Mutters Archives, 1841.] 



On the circulation in the Infusoria. Dr. Erol of Munich, in a letter 

 to Professor Miiller, says, " I have now very often seen and shown to 

 my friends about here a kind of circulation in the Infusoria, a pheno- 

 menon so remarkable that I cannot but wonder that it is not mentioned 

 by any microscopic observer. I find it most distinctly in the Bursaria 

 vernalis, whose abdomen, you know, appears to be quite full of green 

 globules. Of these globules, those which lie near the periphery of the 

 animal are incessantly moving, whether the animal itself be still or not, 

 in an elliptic current upwards and downwards. In this current three 

 or four globules always lie close by one another, and move together with 

 the stream. It has no relation whatever to the vivid ciliary motion 

 that is constantly going on at the outer surface." Heft. 3, 1841. 



On the Development of the Hair. By Dr. G. Simon of Berlin. All 

 the investigations into this subject, which are possessed of any real va- 

 lue, are comparatively recent. For most that is important, we are 

 indebted to the researches of Heusinger, Gurlb, Henle, Mandl, Busk, and 

 Bidder ; but many points have been still left undetermined, to some of 

 which Dr. Simon has directed his attention. 



Heusinger has stated that a black discolouration of the skin precedes 

 the formation of the hair. Simon found this substantiated by the ap- 

 pearance of the skin in the embryos of the pig, and ascertained, as 

 Heusinger had done before him, that this colour is produced by small 

 black granules, which lie very close together. In some embryos this 

 was not perceptible, while in others part of the skin was white, part 

 discoloured. This difference of colour was owing to the presence of 

 white corpuscules in the place of the dark granules. These bodies are 

 formed of small sacs, running from the epidermis in a very oblique 

 direction into the corium, which begin with a narrow neck, and termi- 

 nate in a rounded pouch. They are in hair follicles, and are formed a 

 considerable time before any hair can be observed in them. The only 

 difference between the white and the dark follicle is, that the walls of 

 latter, in addition to being formed of a granular matter, are furnished 

 with a layer of pigment cells. 



At the bottom of the hair sacs of some embryos six inches long, a 

 dark mass was seen, perfectly distinct from the lining of pigment, and 

 closely resembling in form the root of the young hairs. This mass too, 

 was observed in some sacs unfurnished with pigment cells, and was 

 composed of rounded granules in close apposition with each other, and 

 very similar to the pigment cells in the rete malpighii of the human 

 skin. Another circumstance, too, which renders it extremely probable 



