Septembee 27, 1912] 



SCIENCE 



413 



members of an entirely different class of sub- 

 stances, namely, alkaloids. 



Of the alkaloids so far tried theobromine is 

 not suiEciently soluble in sea water to affect 

 the embryos noticeably. The effects of caf- 

 feine and theine' are identical. Nicotine is 

 four times more toxic, but when used in 

 proper concentration produces similar results 

 {M/400 nicotine = il//100 caffeine). 



The effects of these alltaloids is cumulative, 

 {. e., the greater the length of time the em- 

 bryos remain in a solution, the less the con- 

 centration of the latter needed to produce a 

 certain effect. 



In the majority of the experiments, the 

 embryos at about the four-cell stage, were 

 placed in sea-water solutions of the alkaloids 

 and allowed to remain thirty-six hours, then 

 transferred to sea water. 



The very constant effects of these alkaloids^ 

 are the enlargement of pericardium, ear and 

 brain vesicles and ccelom, together with the 

 suppression of the circulation. The heart may 

 or may not beat, and may or may not contain 

 erythrocytes. Erythrocytes are seen in the 

 embryo, but not on the yolk sac. They are 

 often clumped in masses of various sizes 

 along the non-functional blood vessels. Black 

 pigment cells migrate over the lower side of 

 the pericardiiim and red pigment cells over 

 the heart in an abnormal manner. 



Primary cyclopia is extremely rare. In 

 fact, the only cases found were two in the 

 nicotine solutions. However, there are cases 

 of secondary " one-eyedness " due to degen- 

 eration of one of the eyes or fusion of the eyes. 



Many of the alkaloid embryos sooner or 

 later begin to degenerate. Since degeneration 

 occurs in other classes of experiments with 

 Fundulus embryos in which the circulation is 

 suppressed, the lack of a circulation might be 

 considered the cause of degeneration. How- 

 ever, I consider this improbable, since many 

 embryos lacking a circulation show no signs 

 of degeneration, unless the oedema of serous 



^ Considered identical chemically. 

 ^ And of a number of others used since this went 

 to press. 



cavities be considered such. The degenerative 

 effects of alkaloids may not appear until after 

 the period when the circulation is normally 

 established, even though the embryos were 

 removed from the solutions before this period. 

 But this does not prove that degeneration is 

 due to lack of a circulation. 



One eye may degenerate before the other, 

 but usually the degeneration is symmetrical. 

 The degenerating eye becomes irregular in 

 outline and finally its boundary can not be 

 distinguished. The retinal pigment is the 

 only part of the eye substance that remains 

 identifiable in living specimens. In one speci- 

 men the two pigment masses moved from their 

 position in the head and formed an attach- 

 ment to the venous end of the heart. 



In the stronger solutions, the cells over the 

 whole surface of the embryo become loosened 

 at an early stage. A process of de-differentia- 

 tion occurs, and there finally remains but an 

 irregular patch of cells, among which only the 

 pigment cells are distinctive. In this con- 

 dition the embryo may live for many days. 



Similar degeneration may occur as the ef- 

 fect of other poisons, but seems to be more 

 common as an effect of alkaloids. On the 

 other hand, cyclopia is rarer in alkaloid em- 

 bryos than in those treated with certain other 

 substances. Whereas in solutions of ethyl 

 alcohol 100 per cent, of the embryos may show 

 primary defects in the eyes; such occurred in 

 only about one in a thousand of the nicotine 

 embryos. Although thousands of eggs were 

 placed in caffeine and theine, this number is 

 too small to exclude the possibility that 

 cyclopia might occur as frequently as in nico- 

 tine. 



Much has been said for and against the 

 idea of the specificity of the action of various 

 substances on embryos. The data found in 

 the literature indicate that more qualitative 

 and quantitative observations are needed on 

 this subject. Organisms are not simply chem- 

 ical compounds. In studying the mechanism 

 of the effects of chemicals, the structure of the 

 organisms should be especially considered; 

 and not only the morphological structure, but 



