196 THE entomologist's record. 



Amersham with very light apical blotch which was intersected through- 

 out by parallel bars of white. (5) A ^ underside from Oxshott with 

 basal half of forewing clear light yellow. 



Early observations on P. apollo. — Mr. Turner also showed a copy of 

 Jacob Christian Schaffer's work, date 1763, and called attention to the 

 coloured plates illustrating the life-higtory of Parnamus apollo, including 

 figures of the eversible fork on neck of larva, flimsy cocoon for .pupation, 

 structure of prolegs, and details of the curious copulatory pouch ; 

 mostly magnified. 



Irish A. plexippus. — Mr. Frohawk, the specimen of Anoda plexippas 

 captured last year in Ireland. 



Reports on the Season. — Reports on the Season shewed that 

 things were up to date, and generally common. 



;k^eviews and notices of books. 



Sex-linked Inheritance in Drosophila, by T. H. Morgan and C. B. 

 Bridges. Washington. Published by the Carnegie Institution of Wash- 

 ington, 1916. — In the autumn of 1916, at a meeting of the South London 

 Entomological and Natural History Society, Prof. Bateson, one of the 

 greatest of British students of Heredity, and especially of the applica- 

 tion of Mendel's law of inheritance, gave a most intei'esting account of 

 the more recent advances made in America in the study of the inherit- 

 ance of linked characters. Subsequently, by the kindness of the 

 authorities of the Carnegie Institution, Washington, a copy of a work 

 by Professors Morgan and Bridges, Sex-linked Inlieritance in DroHopliila, 

 a detailed report and summary of an enormous number of experiments, 

 has been sent to us for notice in the magazine. 



While it may no doubt b3 assumed that the Mendelian laws of 

 inheritance will probably be proved to be of universal application, yet 

 their satisfactory demonstration in any one organism is by no means 

 frequently an easy matter, owing to the complicated nature of the 

 interrelations of the various characters. In the present state of our 

 ability, which of course rests upon our previously acquired knowledge, 

 objects must be chosen for study which possess certain fortuitous 

 limitations, which will mechanically facilitate not only the easy obser- 

 vation but also the ready manipulation. There must be a capacity for 

 very frequent generation in the subject chosen, it must be easy and 

 inexpensive to breed, a large number of offspring must be produced at 

 each brood, these must possess vigorous constitutional strength, the 

 characters to be dealt with must be " discontinuous," that is, be sharply 

 defined (as in Mendel's peas, smooth and wrinkled, tall or shorty white 

 or purple), and each character, or rather pair of alternative characters 

 ("allelomorph") chosen must be capable of segregation on crossing, 

 that is there must be no contamination one with another in the 

 hybrid. 



The subjects which, up till recently, have been chosen for investiga- 

 tion have possessed these limitations rather less than more, such as 

 Mendel's peas, various plants, species of Lepidoptera, pigeons, fowls, 

 sheep, etc., in all of which objects the above limitations were only 

 present to a degree, and it was not until about seven years ago that 

 Professor Morgan and his talented assistants met with the small 

 Dipterous B-j Drosopltila ampelophila, which apparently is endowed with 



