Author Description

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt:...amitosis. On the other hand, there can be little doubt that the conditions which, according to the hypothesis, favor amitosis are present in the testes. The development of each testis involves the formation of a relatively enormous amount of nuclear and cytoplasmic material and each prologottid contains hundreds of testes. Failure to attain equilibrium might be expected here if anywhere. Indeed the frequent degeneration of masses of cells in the testes (Child, '07b) seems to indicate very clearly that insufficiency of nutrition and failure to attain equilibrium exist, especially as this degeneration is much more frequent in some chains and proglottids than in others. Apparently some cells are forced so far from equilibrium that they can no longer exist. It has been noted (Child, '07b) that such degeneration of cells was not observed in stages from the beginning of the growth-period to the spermatid. It is not improbable that cells which once enter upon the growth-period possess sufficient energy to obtain nutritive material, notwithstanding the demands of their rivals in earlier stages, but it is also possible that some of these cells are so far from a condition of equilibrium that they cannot go through the maturation mitoses following the growth-period. Such cells are probably those in which fragmentation occurs. Certainly the process of fragmentation in the spermatocytes (Child, '07b) presents no difficulties to such an interpretation. In it most of the nuclear substance disappears and a few small nuclei are formed from what might almost be regarded as the debris of the original nucleus. Apparently the old nucleus is no longer able to exist as a physiological system and small parts of it form new systems. The special form of fragmentation in these cases...