564 NATURAL SCIENCE. ocr.. 



Molecular Constitution of bodies, Chemical Affinity, and the Conser- 

 vation of Energy, there is little doubt that this knowledge will have as 

 important a bearing upon everyday affairs as the great industries that 

 have been founded on our knowledge of non-living matter. 



Colour Blindness. 

 Biologists are already called upon to give advice in many 

 matters of ordinary life, and among the latest subjects submitted for 

 their consideration is that of colour vision. A Committee of the Royal 

 Society of London, composed both of Biologists and Physicists, has 

 presented a report on the subject to Parliament, and this is now issued 

 as a Blue-book. It appears that nearly four per cent, of the males in 

 civilised countries exhibit some defect in colour-perception ; and most 

 of these persons are practically blind to one of the primary colours of 

 the spectrum. Blindness to red appears to be most frequent, while 

 blindness to green is not uncommon, and there is rarely failure to 

 perceive blue. Some people are blind to two colours, and instances 

 are known in which no difference could be recognised between the 

 three primary colours. The industrial importance of such colour- 

 blindness, in relation to marine and railway signalling, is too apparent 

 to require comment ; and the Royal Society's Committee will have 

 done good service if their Report leads to satisfactory legislation. 



The Skeleton of the Voice-Organs. 

 Among the most interesting of recent researches in the develop- 

 ment of the animal organism, are those devoted to the elucidation of 

 remnants of embryonic structures in the adult. The preliminary 

 results of these researches sometimes prove to be rash speculations, 

 and we are occasionally inclined to question the value of such journals 

 as the Zoologischev Anzeiger and the Anatomischev Ameiger, in which they 

 chiefly appear. In the last-named journal of August 27, however, 

 there is a noteworthy publication by Dr. Harris G. Wilder on the 

 cartilages of the larynx in the Amphibia, in which some striking, novel 

 views are advanced for examination. It is well-known that at least 

 four of the pairs of bars that support the gills of the young tadpole 

 become fused together to form the hyoid plate supporting the tongue 

 of the adult frog. The question now arises as to what happens to the 

 fifth (or hinder) pair of gill-arches when the time arrives for their 

 disappearance or modification. Dr. Wilder believes his researches 

 will show that these elements are transferred to the voice-apparatus, 

 and become the arytaenoid cartilages of the larynx. Du Bois has 

 already determined that the thyroid cartilage of the larynx is derived 

 from part of the second and third gill-arches ; and Dr. Wilder's new 

 view is further rendered probable by the fact that no animal possesses 

 both the fifth gill-arch and the arytaenoid cartilages, exhibiting only 

 one or the other supplied by one and the same nerve. 



