ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 397 



" annual ring," the growth which takes place in the complete summer 

 and winter) increases from the head to the adipose fin, and then di- 

 minishes towards the tail. A similar increase and decrease is found both 

 on the dorsal and ventral sides of the lateral line. In a comparison of 

 scales taken from positions at corresponding distances ttom the head on 

 both the dorsal and ventral sides of the lateral line, it is seen that, as a 

 general rule, the scales of the dorsal side have fewer annuli in each pero- 

 nidium than the scales from the ventral side. No evidence of different 

 tvpes of annuli was found. 



c. G-eneral. 



Growth of Nerve-cells.* — M. Miihlmann has studied the structure 

 and growth of nerve-cells in various Mammals. The cytoplasm differs 

 from that of other tissues in being provided with a basi-chromatin sub- 

 stance, which differs from that of the nucleus. At first it occurs as 

 diffuse granules, but it soon collects into areas of tigroid substance. In 

 the living cell the tigroid substance is probably in solution, becoming 

 granular in the rigor mortis of the cell. It must have an important 

 physiological significance, since it is in close relation to the neurofibrils 

 and fills the meshes between the bundles. When the tigroid substance 

 is well represented, irregularly disposed fatty granules appear in the 

 cytoplasm. In the course of growth these increase in amount and become 

 pigmented. In advanced age the lipoid character may be lost and the 

 pigmented character remain. 



In the nucleus there is at first an abundant content of nuclein. This 

 is gradually reduced, passing from several nucleoli to one. It then 

 forms an external envelope, dissolves in the nucleolus, and disappears. 

 Lipoidosomes are formed in the nucleolus, analagous to those in the 

 cytoplasm. But they do not accumulate with increasing age. They 

 disappear in youth and leave vacuoles behind. 



Effects of Radium on Living Substance.f — E. D. Congdon has 

 made various experiments to test the influence of radiations of radium. 

 Beta radiations, from 100 mgs. of radium of one thousandth the strength 

 of the pure bromide, in a cubical mass, placed from 1 to 2^ cm. from 

 Drosophila eggs for twenty-four hours, produced a retarding effect on 

 growth. It was more intense the nearer the eggs were to the radium. 

 At greater distances, up to 5 cm., there was some evidence of slight 

 acceleration. Secondary Ijeta radiations (slow electrons) produced a much 

 stronger effect than primary radiations (rapid electrons) of like intensity. 



When pieces of regenerating IhibuJaria hydranths were exposed to 

 similar radiations for periods up to three days in length, the shorter ex- 

 posures were found to accelerate regeneration and the longer to retard. 

 The degree of retardation increased slowly with lengthening exposure ; 

 but the degree of retardation relative to the length of exposure decreased 

 witli lengthening exposure. 



Hermaphroditism in Frogs. | — Davenport Hooker has reviewed the 

 recorded cases, and finds that live conditions occur :■ — ^1. Males with 



♦ Arch. Mikr. Anat., Ixxvii. (1911) Heft 3, Abt. i., pp. 194-231 (1 pi.). 



t Bull. Mus. Comp. Zool. Harvard, liii. (1912) pp. 347-58 (8 figs.). 



X Arch. Mikr. Anal., Ixxix. (1912) Heft 4, Abt. ii., pp. 181-200 (1 pi. and 1 fig.). 



