SPECIAL PHYSIOLOGY OF SEX AND REPRODUCTION. 259 



an unending series of individuals, each as old as the species 

 itself, each with the power of living on indefinitely, ever divid- 

 ing 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 multiphcation 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 hable to be devoured as those of higher 

 degree. In relation to the environment, however, their sim- 

 plicity 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 higher animals (see fig. p. 193), endure desiccation 

 with successful patience, which is rewarded by a rejuvenescence 

 when the rain revisits the pools. But the doctrine of the 

 *'immortahty of the Protozoa" refers to a defiance of natural, 

 not violent, death. 



The psychological objection that the mother psyche is really 

 extinguished 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 residual 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 possibifity, that in the suctorial Acinetae, 

 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 



