426 STELLA B. VINCENT 



and about Cambridge. The tame rats were taken from a strain 

 bred for ten years past in the Harvard Zoological Laboratory. 

 There were two types of this strain, one of which was known to 

 have more wild blood than the other. These rats were graded 

 from to 5 in savageness, wildness and timidity. The indications 

 of savageness were biting, exposing or gnashing teeth, jumping at 

 hand or forceps and squeaking. The signs of wildness were 

 attempts to hide, excited running, squeaking, urination, defeca- 

 tion. Timidity was indicated by attempts to avoid experimenter, 

 chattering or gnashing of teeth, cowering, urination and defeca- 

 tion. Wild males were crossed with tame females and the off- 

 spring, 78 in number, bred by others, were then tested three to 

 five times by the experimenter who did not know the genetic 

 relations of the rat and therefore was entirely unprejudiced. 

 The results showed (a) diminishing savageness, wildness and tim- 

 idity; (b) sex differences; (c) marked differences from the original 

 stock. Another cross, where the tame female strain had back 

 of it wild blood, showed this wild blood in the first generation. 

 The author thinks the tests prove conclusively that savageness, 

 wildness and timidity are heritable behavior complexes. 



Birds. Shepard and Breed (52) compare the relative sig- 

 nificance of maturation and use in the development of the peck- 

 ing instinct of birds. The chicks were incubated absolutely in 

 the dark, taken from the incubator to the dark room at night, 

 fed by hand in the dark for several days, and finally were 

 taken out for experimental observation on the fourth and fifth 

 days. The number of complete pecking reactions in 50 was 

 taken as a standard of accuracy. When brought into the room 

 the chicks were temporarily phototropic. As compared with 

 the normal groups pecking from birth, the points noted were 

 (a) the uniformly poor initial records and (b) the rapidity with 

 which normal accuracy was attained. At the beginning the 

 efficiency of the chicks was 18 per cent below normal but in two 

 day's practice, in which there was no excessive practice due to 

 delay, the birds reached the normal standard. Hence, the experi- 

 menters believe, it may be assumed that the curve after the 

 first two days is mainly a curve of maturation. 



We have in the article by Craig (14) a continuation of the 

 work reported in 1911 on the stimulation of ovulation in birds, 

 etc. There are 24 new cases given with all of the essential details, 



