THE MAIOTIC PROCESS IN MAMMALIA 
occur in plants. By this means we have, as explained in our former work, a 
consistent and simple terminology which can be applied with equal precision 
in the case of any animal or plant. At the same time we entirely obviate the 
necessity of using the cumbrous nomenclature which has grown up in the 
literature dealing with this subject, and according to which we find corre- 
sponding elements designated by the terms — Spermatocytes of the first and 
second order ; Ovicytes of the first and second order ; Sporogonia ; Oogonia ; 
Spore mother cells ; Spores ; and the like. 
I.—THE PRE-MAIOTIC PERIOD. 
F"or some time after the first segmentation of the egg the cells whose 
descendants are destined to give rise to the sexual elements, or to form some 
portion of the animal body, are, so far as their cytological characters go, 
all essentially similar ; as regards the peculiarities of their divisional 
phenomena, whether the so-called somatic and reproductive tracts become 
differentiated early, or late, these peculiarities remain constant till the maiotic 
process is initiated in the reproductive series. Or, as sometimes happens 
through the appearance of cancer, and under exceptional conditions among 
plants, maiosis is produced within the elements of the somatic stock. Thus 
the pre-maiotic sexual cells may be viewed as undifferentiated somatic cells ; 
or conversely, and probably more correctly, the so-called somatic elements 
can be regarded as differentiated pre-maiotic cells. 
All the divisional phenomena of the pre-maiotic cells of the early 
sexual tract could be equally well illustrated by observations directed 
upon the ordinary somatic cells of the body, or vice-versa. And, 
notwithstanding the fact that the cells of the soma may become 
specialized, we regard all pre-maiotic elements, whether belonging 
to the soma or to the anlagen of the rc-productive glands, or 
to the mature re-productive glands, as being essentially similar from a 
morphological point of view. Maiotic, as well as pre-maiotic, cells may be- 
come temporarily specialized ; when, for example, archoplasmic vesicles, 
chromatic bodies, and other structures are present. And post-maiotic cells 
may become similarily histologically differentiated, as in the case of the 
spermatozoa. A bundle of spermatozoa is a mass of cells, each of which 
is more specialized histologically than a cartilage cell, or a connective tissue 
element, or even most gland cells. Again, the ordinary somatic functions 
may be discharged by post-maiotic cells, as in the case of the prothalli of 
ferns, and the peculiar morphological characters of the prothallus can be 
assumed by pre-maiotic cells in special cases * 
Consequently from such a point of view as the above the question of 
somatic, or histological, differentiation loses all significance. What remains 
important are the constantly recurring features of the life cycle of the cells of 
animals and plants. The three phases, pre-maiotic, maiotic, and post- 
maiotic : to one of which the cells of any particular tissue invariably belong. 
From this point of view the cells of the soma of any animal, and those of 
the young reproductive series, are both similar, in that they are both pre- 
maiotic in phase. 
' Digby, Miss L. Pro. Roy. Soc, jgos. 
