Allgemeine Biologie und Entwickelungslehre. 



Blakeman, Elderton, Helguero, Pearl, Wissler and Yule contribute papers 

 dealing either with the mathematical theory or the technical methods of biometry. 



Punnett( 2 ) attacks biometrically the problem of the origin of the vertebrate 

 limbs using as material Spinax niger. Data were collected on 10 characters : 

 Number of whole vertebrae, and of half vertebrae, total segments, position of 

 anterior spine, of posterior spine, and of 1st girdle-piercing nerve, the nervus 

 collector, the post- girdle nerves, the number of fin-rays in the pelvic fin, and 

 the length of the whole and half vertebral series. There is a definite sexual 

 dimorphism with respect to the meristic characters. Male embryos are much 

 more variable than male adults, the indication thus being that there is a 

 stringent selection of cf. In the Q there is little difference in the variability 

 of embryos and adults, indicating that the selection is less stringent than in 

 the case of the rf . Dealing with adults only there is approximate equality 

 of variability in characters involving the spines and vertebral column, while in 

 characters connected with the position of the ventral fins the Q? are the more 

 variable. The biometrical results are strongly in favor of the view that the 

 limbs owe their position to a process of homoeosis rather than to a process of 

 inter- or excalation of vertebral segments. The results thus point towards the 

 gill-arch rather than the side-fold theory of the origin of the limbs. Study 

 of the parental (maternal) and fraternal correlations clearly demonstrated that 

 the meristic characters studied are inherited. The author inclines to the view 

 that the values of these correlations indicate that the inheritance in this case 

 follows Mendel's laws rather than the law of ancestral inheritance. -- Pearson (^ 

 shows that no test between the two laws can be made on the basis of the 

 material available here. 



Schuster details the results of breeding experiments with Mus. His con- 

 clusions are : "with regard to the characters, colour -productiveness and albinism 

 the mice under consideration here behave in complete accord with Mendel's 

 laws, both with regard to dominance and segregation. If one considers the 

 nature of the colour and the question as to whether it is distributed uniformly 

 or is marked with white there is nothing in my results incompatible with 

 similar behaviour with regard to these characters also". 



Morgan ( 2 ) attempts to interpret Cuenot's latest results on Mendelian inheri- 

 tance in Mus by assuming that characters united in the heterozygote "do not 

 separate again, but alternately dominate and remain latent". The author 

 questions "the assumption of the so-called purity of the germ cells, by means 

 of which modern writers are explaining the Mendelian results". 



In a detailed and extensive paper G. Allen presents the results of his studies 

 on the inheritance of coat color in Mus. The introductory sections of the 

 paper deal with (a) the varieties of Mus, (b) the methods used in conducting 

 the experiments and keeping the records, and (c) a general statement of 

 Mendel's principles of heredity. The author records the observation of a 

 specimen of the so-called rhinoceros variety of Mus, and gives evidence to 

 show that this is not a true variety, but represents a pathological condition. 

 Complete albinism is recessive towards either partial or complete pigmentation, 

 and behaves in segregation according to Mendelian expectation. Partial albi- 

 nism is a condition in which the pigment is reduced around definite body 

 centres, leaving unpigmented areas between these centres. There are 5 such 

 pigment centres on either side of the body in Mus. A similar arrangement 

 of pigment centres occurs in other spotted mammals. Partial albino individuals 

 breed true to that condition. Partial albinism is recessive toward complete 

 albinism, and tends to be recessive to complete pigmentation also, though the 



