PHYSIOLOGY OF SEX AND REPRODUCTION. 



39 



end to their development which can be likened to death, nor is the 

 rise of new individuals associated with the death of the old. In the 

 division the two portions are equal, neither is the older nor the 

 younger. Thus there arises an unending series of individuals, each as 

 old as the species itself, each with the power of living on indefinitely, 

 ever dividing but never dying." Ray Lankester puts the matter 

 tersely, "It results from the constitution of the protozoon body as a 

 single cell, and its method of multiplication by fission, that death has 

 no place as a natural recurrent phenomena among these organisms." 

 Some limitations must be noticed, which make this idea of pristine 

 immortality yet more emphatic. It is only asserted that the Protozoa 

 escape ' ' natural death, ' ' a violent fate may of course await them like 

 any other organisms. They have no charmed life, being as liable to 

 be devoured as those of higher degree. In relation to the environ- 

 ment, however, their simplicity gives them a peculiar power of avoiding 

 impending destiny. The habit of forming protective cysts is very 

 general, and thus enwrapped they can, like the ova and a few of the 

 adults of some of the higher animals (see fig. p. 179), endure desicca- 

 tion with successful patience, which is rewarded by a rejuvenescence 

 when the rain revisits the pools. But the doctrine of the "immor- 

 tality of the Protozoa" refers to a defiance of natural, not violent, 

 death. 



The psychological objection that the mother psyche is really extin- 

 guished when she divides into two, intrudes a conception which is 

 hardly applicable. The individualities are doubled, nothing is really 

 lost. Most seriously difficult are those cases where the protozoon 

 produces a series of buds, spores, or division units, and leaves a resid- 

 ual core or unused remnant behind to die. But in regard to the 

 gregarines, for instance, where such a remnant is left, it has been fairly 

 answered that the residue is rather a kind of excretion than the parent 

 left to perish after its reproductive sacrifice. Weismann is, however, 

 willing to admit the possibility, that in the suctorial Acineta, and in 

 the parasitic gregarines, which are both somewhat removed from the 

 normal protozoon type, there may be cases of true mortality. 



Another point in regard to which experts differ, is whether the 

 Protozoa are really quite self-recuperative. They suffer injuries, they 

 necessarily waste, portions are used up and may be ejected. The 

 question then arises, Are those acquired defects obliterated, or do they 

 become intensified ? Is the wasting only a local death, or is it the 

 beginning of a true senescence? This is a question which can only 

 be answered by observation; a priori reasoning is here futile. The 

 most serious criticism of Weismann' s view is due to Maupas. Already 

 we have noted his important result, that conjugation is essential to 



