444 EDWARD E. WILDMAN 
posed of ‘mitochondria’ that led Benda, Duesberg and others to 
claim for these bodies a continuity and significance in heredity 
quite equal to those of the chromosomes. 
But Lillie finds that the middle-piece never enters the egg in 
Nereis. This discovery, therefore, renders this interpretation of 
the importance of ‘mitochondria’ exceedingly doubtful. On page 
427 this author discusses this question as follows: 
The only characteristic thing about the cytoplasmic. elements intro- 
duced by the spermatozoon is their great variability as to quantity and 
character in different animals. In Ascaris a very large quantity of cyto- 
plasm containing characteristic plastosomes is introduced, as Meves 
has shown. In many, probably most, forms with flagellated sperma- 
tozoa, the entire spermatozoon enters; in some echinids the tail is left 
without, and in Nereis both tail and middle-piece fail to enter; and turn- 
ing to plants, in phanerogams, apparently nothing but the nucleus is 
eventually concerned. There is nothing on the cytoplasmic side to 
correspond with the regularity of the nuclear phenomena in both ani- 
mals and plants. In such precise phenomena as those of inheritance a 
mechanism of equal precision is to be expected, and it must be admitted 
that on the cytoplasmic side no such mechanism has been discovered. 
Moreover, as the laws of inheritance are the same for both animals and 
plants, a similar mechanism must exist for both, and such has been dis- 
covered only in the nuclei of the gametes. There is bad logic in the 
assumption that whatever parts of the spermatozoon enter the egg 
are necessarily concerned in the mechanism of transmission in inherit- 
ance, and the view that the cytoplasmic elements of the male gamete 
are concerned primarily in accessory functions of fertilization, such as 
locomotion and penetration, is still well founded. 
The nature and function of ‘mitochondria’ or plastochondria 
I believe the cases just cited argue strongly against Meves’ 
interpretation of the importance of the plastochondria in Ascaris, 
and of the ‘mitochondria’ in other forms. If these plastin gran- 
ules are of such great importance in heredity as Meves, Benda, 
Duesberg and others believe, it is difficult to understand why 
such a considerable proportion of them should be lost by the 
sperm during the course of its development. In Nereis we see 
the loss of this material just before fertilization occurs; but in 
many forms it takes place earlier. It has already been stated 
that a reduction in the amount of cytoplasm occurs in the young 
