This distinction arose as soon as the species was taken into the hothouse, but when the modified individuals were put back into the original conditions, a lower temperature and scanty food-supply, the next generation returned to their original form. After being cultivated for two years and about 40 generations in the more favourable conditions, when similarly put back into the lower temperature with scanty food the _first generation_ born in these conditions was helmeted like the modified parents. Woltereck is of opinion that the ova were still unformed at the time the parents were put back, and the influence of the favourable conditions upon the unformed ova he speaks of as a "prae-induction." The effect never extended beyond the one generation, after which the strain returned to its original state. The fact that the influence on the offspring was not manifested at first led Woltereck to expect that by more prolonged cultivation in the favourable conditions a further extension of this influence would be produced, but this expectation was never fulfilled, though the attempt was made again and again. Similar experiments were made with _Hyalodaphnia cucullata_, which is far more sensitive to cultural influences, and in nature manifests a considerable elongation of the helmet as a seasonal modification, but the results were essentially the same as in the preceding case, no modification extending beyond the first generation born after the restoration to _normal conditions_.[5] The only criticism of these extremely interesting results which suggests itself is that perhaps the original appearance of the modification was not in reality due to an _accumulated_ effect of the conditions, but to some change in the conditions themselves which was not noticed. It is difficult to see how length of time or even the lapse of several generations could have so specific an effect on the race. It is no doubt often vaguely supposed by many that a long period of time may be necessary for the effect of climate or of other environmental conditions to be produced in an organism which does not thus respond at first. I have never been able to see any reason for this opinion nor how it is to be translated into terms of physiological fact, and I imagine that in those cases in which the lapse of time is really required for the production of an effect, the influence of the prolongation is rather on the conditions than on the organisms. The response of the organisms thus probably indicates not that the creature is at length feeling the effects because of their accumulated action on itself, but that the conditions have at length ripened.