ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 225 



diffused througli it. It is possible, but the question must still remain 

 an open one, that it is merely a massive nucleus. It gradually 

 separates itself from the neighbourhood of the germinal vesicle, and 

 passes to the periphery of the yolk ; it becomes more granular, and 

 undergoes disintegration ; its elements, divided into small globules, 

 independent of one another, are in parts absorbed by the yolk, or 

 gradually become merged in the superficial granular protoplasm. The 

 vitelline nucleus may, therefore, be looked upon as a centrifugal 

 element, which tends to eliminate itself or to lose its " autonomy." 

 Sabatier regards it as an element of male polarity, which is destroyed 

 as such to accentuate and complete the sexuality of the female cell. 



Restoration of Limbs in Tarantula.* — H. C. McCook recently 

 exhibited a tarantula which had been kept in confinement nearly a 

 year, fed during winter on raw beef and in summer on grasshoppers. 

 In the spring it cast its skin by a laborious process, in the course of 

 which it lost one foot and two entire legs. Last summer again, 

 during the latter part of August, the animal moulted; the moult 

 being a perfect cast of the large spider — skin, spines, claws, the most 

 delicate hairs all showing, and their corresponding originals appearing 

 bright and clean upon the spider. The moulting occurred during 

 Dr. McCook's absence, but was just finished when he returned. When 

 the cast-off skin was removed it showed, as might be supposed, the 

 dissevered members to be lacking. But on looking at the spider 

 itself, it was seen that new limbs had appeared, perfect in shape but 

 somewhat smaller than the corresponding ones on the opposite side of 

 the body. The dissevered foot was also restored. The loss of the 

 opportunity to see the manner in which the legs were restored duriug 

 moult was greatly regretted ; but we have some clue from the careful 

 and interesting studies of Mr. Blackwall. Several spiders whose 

 members had been previously amputated, were killed and dissected 

 immediately before moulting. In one of these the leg which was 

 reproduced was found to have its tarsal and metatarsal joints folded 

 in the undetached half of the integument of the old tibia. Another 

 like experiment was made with an example of Tegenaria civilis. The 

 reproduced leg was found complete in its organization, although an 

 inch in length, and was curiously folded in the integument of the 

 old coxa, which measured only 1/24 in. in length. Dr. McCook's 

 tarantula had lost both legs close up to the coxte, and in the moult 

 the hard skin formed upon the amputated trunks was wholly unbroken, 

 showing that the skin had been cast before the new leg aj)peared. 

 We risk nothing in inferring that, as in the case of Blackwall's 

 Tegenaria, the rudimentary legs were folded up within the coxae, and 

 appeared at once after the moulting, rapidly filling out in a manner 

 somewhat analogous to the expansion of the wings in insects after 

 emerging. 



Morphology of Plumicolous Sarcoptidse.f — E. L. Trouessart 

 and P. Megnin have a second note on this subject, in which they 



* Proc. Acad. Nat. Sci, Philad., 1883, pp. 196-7. 

 t Comptes Kendus, xcvii. (1883) pp. 1500-2. 



