RECENT ADVANCES IN SCIENCE 649 



(Jour. Exper. Zool. Oct. 19 16), when compared with careful 

 controls and norms, show the following : Thyroid feeding 

 produces a decided hypertrophy of the heart, liver, spleen and 

 kidneys and suprarenal glands ; thyroid in sub-toxic doses, 

 thymus, hypophysis, and pineal no appreciable result. 



Lastly in Man a " Detailed Study of Superficial Characters 

 of the Brain in Twins of the Same Sex and also other Points " 

 made by Sano (Phil. Trans. Roy. Soc. B, No. 349, 191 6) sup- 

 ports Galton's observations on the functional similarities. And 

 Kernan has described " The Chondrocranium of a 20 mm. 

 Human Embryo " (Jour. Morph. Sept. 191 6), which is inter- 

 mediate between the 18*5 mm. and 23 mm. embryos of Von 

 Noorden. 



General. — Four of the general papers deal with more or 

 less cytological problems. Harvey has provided a useful 

 article in " A Review of the Chromosome Numbers in the 

 Metazoa " (Jour. Morph. Dec. 1916), in which is given a list 

 of all the various and in some cases contradictory chromosome 

 numbers that have been published since Van Beneden's work 

 in 1883 up to 191 5. It includes only the Annelida, Arthopoda, 

 and Ccelenterata. A method for " The Calculation of Linkage 

 Intensities " is given by Emerson (American Nat. July 191 6). 

 He claims that the formulae suggested afford a convenient 

 method of approximating gametic ratios from zygotic series 

 when the observed frequencies are in fair accord with a series 

 based on a given formula, or the formula of Bateson and 

 Punnett. Should the observed frequencies be far from this 

 type no method gives a close fit between observed and calcu- 

 lated results. In the same journal Muller discusses " The 

 Mechanism of Crossing Over." 



Packard has carried out experiments on " The Effect of 

 Radium Radiations on the Rate of Cell Division " (Jour. 

 Exper. Zool. Aug. 191 6). Such radiations have an appreciable 

 effect and it is suggested that such results are due to their 

 direct action upon the endoenzymes. These in their turn 

 affect all the chemical processes in the cell and also the rate 

 of cell division. 



Lastly Werber furnishes a long account and discussion of 

 " Experimental Studies on the Origin of Monsters " (ibid. 

 Nov. 1916). He states that in general the results of such 

 experiments go far towards justifying the hypothesis on which 



