444 SUMMARY OF CURRENT RESEARCHES RELATING TO 



left segment, includes all the derivatives of the intermediary vesicle of 

 this segment. It includes not only the canal of the excretory organ 

 (the " nephridium " of Hatschek sensu stricto), but also the portion of 

 the mesodermic segment that is represented in the adult organ by the 

 " chambrettes a solenocytes." The general thesis is that the nephridium 

 of the buccal metamere and the excretory organs of the branchial 

 metameres are homodynamous. 



Hybridisation of Wolf and Dog.* — Paul Paris gives a short account 

 of the evidence in regard to the crossing of wild she-wolf by a domestic 

 dog in 1879 in the department of Cote-d'Or. Two of the young ones 

 showed some of the distinctive characters of the father , 



Plumage of Hybrids between Guinea Fowl and Fowl.f — M. F. 

 Guyer finds that the plumage of these hybrids is in some cases atavistic, 

 showing alternate light and dark chevrons, which is characteristic of 

 some types like Polyplectron and Agelastes, and may have been the 

 primitive plumage of the pheasant family. 



Development of Penguin.^ — D. Waterston and A. Campbell Geddes 

 have studied a series of embryos of Pyyoscelis papua and P. adelise 

 brought home by the " Scotia" Expedition. They contrast the penguin 

 embryo with that of the duck. " The fore limb of the penguin is, in its 

 mesoblastic structures, definitely progressive, whereas the mesoblastic 

 portion of the duck's wing is relatively regressive." In some notes on 

 the adult birds, attention is directed to the extraordinary convexity of 

 the curve of the neck. The trachea and oesophagus enter the thorax 

 on a plane posterior to the cervical spines. The convexity may be 

 " useful to the birds by increasing water displacement anteriorly, and 

 permitting the head and beak being carried without undue fatigue on 

 the long ocean voyages which the birds undertake." 



b. Histolog-y- 



Nuclear Structured— H. Stauffacher has studied embryonic liver 

 cells and vegetable cells. The oxychromatic matrix-substance of the 

 nucleolus is continuous by internal nuclear bridges with the oxy- 

 cliromatin of the nucleus, and that with the oxychromatin of the 

 cytoplasm. The basichromatin has always an oxychromatin foundation ; 

 in the nucleoli it arises from the oxychromatin ; it passes into the 

 nucleus, and thence, as cytomicrosomes, into the cell-substance. 



The so-called centrosome consists of basichromatic material. It is 

 not an individualised structure, but a local differentiation of protoplasm. 

 It is passive in cell-division. The division of the nucleus is not pre- 

 ceded by a division of centrosomes. The spindle figure is due to the 

 oxychromatin meshwork of nucleus and cytoplasm. 



Relations of Nucleus and Cytoplasm. || — W. Knoll has studied this 

 question in the leucocytes of the blood and bone-marrow. There are 



* Bull. Soc. Zool. Prance, xxxv. (1910) pp. 58-9. 

 t Bull. Mus. Hist. Nat. Paris, No. 1, 190.), pp. 3-5 (2 figs.). 

 X Trans. Roy. Soc. Edinburgh, xlvii. (1909) pp. 223-44 (3 pis.). 

 § Zeitschr. wiss. Zool., xcv. (1910) pp. 1-119 (2 pis. and 3 figs.). 

 || Tom. cit., pp. 120-90 (1 pi.). 



