530 SUMMARY OF CURRENT RESEARCHES RELATING TO 



logically independent of each other, and may be differently coloured in 

 the same individual. 



Pied patterns among many wild species have been brought about 

 through the areal reduction of these pigment patches in a definite way, 

 so that the white markings resulting as breaks between the reduced 

 patches have become fixed, and form a permanent part of the normal 

 pattern. 



In several wild species this development of white markings is shown 

 to be even now taking place, but the amount of pigment-reduction is 

 still fluctuating, so that the white markings vary much in extent in 

 different individuals. 



The development of such white markings takes place probably 

 little by little, so that the departure from the normal type is not so 

 great as to arouse antagonism against the varying individual on the 

 part of others of its species. Also, the slow rate of the change allows 

 the species to become accommodated to any disadvantage that might 

 concomitantly arise. 



The converse of this centripetal style of pigmentation is present in 

 many species, and results in pigmentation (commonly black) at the ex- 

 tremities or along lines where primary breaks occur in the centripetal 

 form, namely, at the tip of the nose, ears, tail, or toes. The black 

 dorsal stripe may also be due to centrifugal pigmentation. Patterns may 

 develop, as in certain antelopes, by a white break between patches of the 

 two types. 



Study of Hooded Fowls.* — Fr. Neumann has made an anatomical 

 study of the hooded fowls of the Houdan breed. A large tuft of 

 feathers decorates the head ; the comb is much reduced in the hens, 

 less so in the cocks. It is of the " butterfly type," with two lateral 

 lobes. The skull is raised in the region of the frontals. Below the 

 comb there are sometimes large vesicles containing serous fluid. All 

 the Houdans have five toes. 



The most noteworthy peculiarity is the special development of 

 the brain. The cerebrum is greatly enlarged anteriorly, and this is 

 sometimes further increased by hydrocephalus. Several investigators 

 have referred the peculiarity of the brain to hydrocephalus, but cases 

 are known with no hydrocephalus, but with the peculiar shape as 

 marked as usual. 



The telencephalon has an unusual tendency to grow in the direction 

 of the longitudinal axis. The corpora striata increase in thickness in 

 their rostral portion mainly. There is an arching over the olfactory 

 lobes. As the caudal portion of the cerebrum is poor in cerebral 

 substance, the cerebrum becomes narrowed posteriorly, and a kind of 

 neck is formed, which slightly separates off the cerebrum from the rest 

 of the brain. This is increased by a slight elongation of the thalamen- 

 cephalon. The skull is transformed in correlation with the change in 

 the shape of the brain. This is particularly the case in the region of 

 the frontals. Another peculiarity is in the vascular supply. The 



* Jen. Zeitschr. Naturw., lii. (1914) pp. 209-68 (1 pi. and 42 figs.). 



