ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 455 



finally abandoned. It is probable that both series of changes are effects 

 of some more deep-seated ovarian phenomena. 



Artificial Production of Spina bifida in Frog.* — W.'M. Baldwin 

 has sought by experimental methods to throw light on the familiar 

 question whether the fertilized ovum is a composite organization of 

 formative substances (or the chemical progenitors of primordia distri- 

 buted in a definite way), or is a unicellular organism without pre-localized 

 differentiated formative substances or primordia, but with the specific 

 capacity of forming " ferments " and primordia at successive genetic 

 stages. Recourse was had to ultra-violet rays of such a degree of 

 intensity as to cause the disorganization of the cytoplasm in from one 

 to thirty seconds, and of such a degree of concentration as to influence a 

 limited surface. 



The killing of a small localized area of the yolk hemisphere or of the 

 region of the equator of the frog's egg produces invariably the condition 

 of spina bifida in the embryo.^ It is further shown that the formative 

 substances of the neural tube do not lie either in the yolk hemisphere 

 or along the equator of the frog's egg, but are wholly restricted to the 

 pigmented half of the egg. They attain their definitive positions by a 

 process of backward migration, the rate of which is synchronous with 

 that of the backward progression of the dorsal lip of the blastopore. 

 The destructive action of the ultra-violet rays results in an upset of the 

 synchronism of the two factors, i.e. differentiation of the neural primordia 

 and approximation of the lips. The former proceeds at its normal 

 tempo, while the latter is retarded. Consequently, the former, always 

 restricted to the pigmented hemisphere, come to lie along the equator 

 and are later carried towards the median plane by the subsequent 

 approximation of the lips, but the half-tubes, having already differen- 

 tiated into whole tubes, do not subsequently fuse. The causative forces 

 in the production of spina bifida seem referable to an upset of a specific 

 substance in the ess. 



J ae>' 



Spawning of Black Bass.f — B. A. Bensley, in an interesting report 

 on the fishes of Georgian Bay, gives an account of the spawning of 

 Micropterus dolomieu. The spawning is usually during June. The 

 male makes the nest — a shallow basin, 15 or 20 in. in diameter, 

 fanned out of the weedy or pebbly bottom, and fully cleaned of all 

 debris. The bottom of the nest may be of clean rock or pebbles, 

 but is more often of short stems of the aquatic plant Eriocaulon, 

 which forms an ideal surface for the attachment of the eggs. The 

 male swims out into the deeper water and drives a selected female 

 before him. She swims into the nest and extrudes the eggs, a few 

 (10 to 12) at a time. The male sheds milt at corresponding intervals. 

 There are marked differences in the coloration of the two sexes at 

 the spawning time. After the spawning, which lasts for a half- 

 hour to three hours, the female leaves the nest or is driven forth. The 

 male mounts guard, fanning the eggs from time to time, and driving off 



* Anat. Record, ix. (1915) pp. 365-81 (16 figs.). 



t Contributions Canadian Biology. Department Fisheries, Ottawa, Fasciculus 

 ii. (1915), pp. 1-51 (2 pis. and 6 figs.). 



