"26 SUMMAEY OF CUEKENT RESEARCHES RELATING TO 



Permanent Forms among Chromosomes of Different Animals.* — 

 .J. E. S. Moore iind G. xlrnold have investigated the forms of " hete- 

 rolytic geniini " in man, rat, newt, cockroach, etc. There are permanent 

 structural types in the gemiui of different organisms. In any particular 

 form the numbers of gemini of each type have a constant numerical 

 relationship to each other. Certain types of gemini appear to be 

 common to all the widely separated forms studied. The number of 

 different types of gemini is less in tlie phyletically oldest form examined 

 — the cockroach. 



Both in regard to the permanent types of gemini and their nu- 

 merical relationships, as well as \\ath respect to the numerical constancy 

 in the chromosomes themselves and their periodical reductions, we are 

 face to face with constant arrangements in the parts of the unit of living 

 substance (the cell) which seem to underlie and to be quite independent 

 of those external interactions that are supposed to have helped to l)uild 

 the grosser features of living things. 



The existence of different types of gemini implies substantive 

 differences between the chromosomes that can unite to form the different 

 kinds. 



The present position may be in part summed up as follows. In the 

 fertilised egg the })aternal and maternal chromoscmies divide inde- 

 pendently on the spindle of the first segmentation figure. They go on 

 dividing in a similarly independent manner throughout the soma, and 

 during the pre-maiotic history of the reproductive elements themselves. 

 in the synapsis which ushers in the maiotic phase the chromosomes unite 

 in pairs, and in those cases hitherto examined only certain individual 

 chromosomes are capable of uniting with one another to form differing 

 groups of gemini. In each of these groups the number of gemini is 

 more than one, and it varies in the different species hitherto studied. 



Culture of an Artificial Cell.f — Stephane Leduc has studied the 

 phenomena exhibited by an artificial cell — a " granule " of sulphate of 

 copper, saccharose, and water, placed in an a(|ueous solution containing 

 ferrocyanide of potassium, salt, gelatin, etc. The granule surrounds 

 itself with a membrane of ferrocyanide of copper, permeable to water and 

 certain ions, but impermeable to the sugar which it encloses, and which 

 produces in the granule the strojig osmotic pressure determining alisorp- 

 tion and growth. There is " nutrition by intussusception," " organisa- 

 tion" — in the form of "stem," "leaves," and " terminal organs," — a 

 circulatory apparatus, and growth. 



c. 



General. 



Nervous System of Vertebrates.:}: — J. B. Johnston has given a con- 

 nected account of the nervous system of Vertebrates, especially in its 

 phylogenetic and physiological aspects. A general text-book on the sub- 

 ject has been a desideratum for many years, and Professor Johnston's 

 volume is very welcome. 



* Proc. Roy. Soc. London, Series B, Ixxvii., No. B521 (1906) pp.563-70 (2 pis.). 

 t Comptes Rendus, cxliii. (1906) pp. 842-4 (2 ftgs.). 



X The Nervous System of Vertebrates. Philadelphia, 1906, xx. and 370 pp., 

 180 figs. 



I 



