.rs 



2 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Hyperdactylism in Houdan Fowls.* — Marie Kaufmann-Wolf gives 

 a precise account of a large number of cases, devoting particular atten- 

 tion to the development. Among the general results of the investiga- 

 tion the following may be noted : (1) Hyperdactylism in fowls is a new 

 departure not atavistic ; (2) there are indications of mirror-symmetry 

 in the hyperdactylous conditions : (3) the cause is endogenous, not 

 extrinsic, e.g. not due to amnion-threads. 



Fault-bars in Feathers.f — 0. Riddle finds that fault-bars (weak 

 areas interrupting the fundamental barring), are due to malnutrition. 

 They may be produced by feeding birds on Sudan iii., by mechanical 

 injury of the feather germs, by bad sanitation, parasites, etc., and by 

 the use of amyl-nitrite to reduce blood-pressure. They are normally 

 laid down at night, wbeu blood-pressure is normally low. The structur- 

 ally weakened areas tend to be less pigmented. " The reduced 

 nutrition, brought about daily by the minimum blood-pressure ; the 

 disadvantageous position, in relation to the blood, of the pigment aud 

 1 larbule elements of the feather ; together with the very rapid rate at 

 which feathers grow, furnish the complex of conditions which bring 

 unfailingly into existence a fault-bar, and to a more or less appreciable 

 extent a light fundamental bar, at perfectly regular intervals in the 

 entire length of every feather formation." " The melanin pigment of 

 the feathers of birds shows, under favourable conditions, quantitative 

 variations of the pigment produced in response to changes in the 

 available food supply. This is an additional evidence that this pigment 

 is not a derivative of haemoglobin, but of the serum or cell proteids." 



Hump-backed Trout.J — James Ritchie discusses a case of abnor- 

 mality — probably congenital — in a common trout (Salmo fario) which 

 showed only 40 vertebra? instead of the usual 56 to GO. The segmenta- 

 tion of the body was normal as regards myotomes, neural spines, and 

 haemal spines, but the region of the centra was reduced as indicated. It 

 is impossible to regard this reduction as due to pathological ankylosis'. 



The possibilities of interpretation seem to range themselves round 

 two alternatives. 1. It may be that certain of the arcualia did not give 

 rise to the usual skeletogenous tissue, within which the ossification of 

 the centra proceeds, and that, therefore, certain of the potential centra 

 never actually existed. That is to say, each of the abnormal internodes 

 in the vertebral column of the specimen described is a true centrum to 

 which one or two neural arches, properly belonging to missing centra, 

 have become attached. The deficiency in the internodes would in tin's 

 case be due to the actual absence of centra. 2. The alternative is that 

 — the skeletogenous tissue of the future centra having been completely 

 formed — a compression in certain regions took place, succeeded by con- 

 tinuous ossification, uninterrupted by nodes. That is to say, the abnormal 

 internodes in the specimen contain the elements of as many centra as there 

 are neural spines, but those elements have not had the opportunity of 

 developing into separate centra. 



* Morphol. Jahrb., xxxviii. (1908) pp. 471-531 (3 pis. and 42 figs.), 

 t Biol. Bull., xiv. (1908) pp. 328-70 (4 pis.). See also Amer. Nat., xlii. (1908) 

 pp. 550-2. % Ann. Scot. Nat. Hist,, 1908, pp. 223-7 (1 pi.). 



