Certain laws of variation. I. The reaction of developing organisms to environment

In a former paper it was shown that the ova of the EchinoidStrongylocentrotus livdus were extraordinarily sensitive to their environmental conditions at the time of impregnation. For instance, by keeping the mixed ova and spermatozoa in water at about 26° or 8°C. for an hour, the plutei obtained after eight days’ development were some 5 per cent, smaller than those from ova kept at about 20° at the time of impregnation. It was even found that the effect produced was nearly as great if the time of subjection to the abnormal temperature were reduced to one or three minutes, though if reduced to ten seconds it was not so great. This latter result was probably due to the time being insufficient for all the ova to become impregnated at the abnormal temperature.