632 SUMMARY OF CUERENT RESEARCHES RELATING TO 



principles, which he applies to the different groups, notably to the 

 mammals. 



The following general statements are elaborated : 1. That the 

 colour-markings of mammals may be reduced to longitudinal stripes, 

 spots, and transverse stripes. 2. That the longitudinal stripes are 

 the oldest form, and that the two follow in course. 3. That the pri- 

 mitive mammalian fauna was a longitudinally striped one. 4, That 

 the males have been first to take on the new forms of markings, while 

 the females hold longer to the older form. 5. That the effects of the 

 law by which the development of the markings takes place from the 

 posterior part of the body toward the anterior part are not so easily 

 traced in mammals as in the case of other groups, such as the Saurians. 



6. That in mammals the development of markings follows a regular 

 course, that is, the longitudinal markings are followed by spots which, 

 in turn, run together, and finally form the transverse or tiger stripes. 



7. That the position of the smallest spot on a mammal is not acciden- 

 tal, but due to the action of generic and philogenetic laws, from which 

 it follows that markings are an available means for the determination 

 of species. 8. That the regularity of the development of markings 

 shows that they arise from constitutional causes. 



The author takes the Viverridfe as the original types of the Carni- 

 vores, and believes that in the hyena, cats, dogs, bears, and weasels, he 

 can trace the form and position of markings possessed by the former. 

 He acknowledges several difficulties, however, in the case of the 

 leopard, jaguar, and other peculiarly spotted cats. He believes that 

 the Ungulates follow the same law in regard to markings as the 

 Carnivores. 



Retina of Ganoids.* — A. Dogiel distinguishes twelve layers in 

 the retina of Ganoids. These are : (1) Pigment layer; (2) Layer of 

 rods and cones ; (3) Granular layer ; (4) Membrana limitans externa ; 

 (5) Outer subepithelial ganglionic layer ; (6) Layer of nervous de- 

 posits ; (7) Layer of stellate cells ; (8) Median ganglionic layer ; 

 (9) Layer of the Neurospongium ; (10) Internal ganglionic layer ; 

 (11) Layer of nerve-fi^bres ; (12) Membrana limitans interna. These 

 elements may be arranged in three groups : (a) Catoptro-dioptric, viz. 

 1 and 2 ; (/3) nervous, viz. 5, 6, 8, 10, and 11 ; and (y) the supporting 

 apparatus. The author describes in detail the various parts. 



Influence of Sea Water on Fresh-water Animals, and of Fresh 

 Water on Marine Animals. | — H. de Varigny records the results of 

 his experiments on the influence of the saline principles contained in 

 sea water. The ova of frogs and tadpoles were employed. 



Sulphate of magnesia (2*20 gr. of which is contained in each litre 

 of sea water), chloride of potassium (0*7 gr. per litre) and chloride of 

 magnesium (3 • 5 gr. per litre) were not found to exercise any injurious 

 influence either on the ova or the tadpoles when the same proportions 

 were separately dissolved in fresh water. Chloride of sodium, how- 

 ever, 20 or 25 gr. of which exists in each litre of sea water, is 

 decidedly hurtful. No ova could be hatched in a solution of 20 gr., 



* Arch. f. Mikr. Anat., xxii. (1883) pp. 419-72 (3 pis.), 

 t Comptes Rendu?, xcvii. (1883) pp. 54-5, 133-G. 



