DAVIS: SPERMATOGENESIS. ts7 
The apical cell seems not to occur in other groups of animals than 
insects, although Lerat (:05) has found peculiar cells in the ovary and 
testis of Cyclops which seem to agree with it in some respects. 
Regarding the function of this cell there are in general two views: 
one, that it is the progenitor of the germ cells; the other, that it has 
nothing to do with the origin of the germ cells, but functions simply as a 
supporting or nurse cell. Verson (89, ’91, ’94) was one of the chief 
exponents of the former view, holding that the other elements of 
the testis are derived from the apical cell by amitotic division. Cholod- 
kovsky formerly (94) held the same view as to the origin of the tes- 
ticular elements, but believed the divisions to be mitotic. His later 
views are mentioned further on. More recently this view of the func- 
tion of the apical cell has given way to the belief that it is a supporting 
element; however, Verson’s interpretation has been revived by Mun- 
son (:06). ‘This author believes that the apical cell (which he calls 
the “grandmother stem cell’’) gives rise in some way to his ‘‘mother 
branch cells,” which immediately surround, and are in close connection 
with the apical cell. These “mother branch cells” undergo repeated 
mitotic divisions, the peripheral (distal) one of the daughter cells of 
each division being budded off to form a ‘primary spermatogone,”’ 
which is the progenitor of all the spermatogonia of a given cyst, while 
the other, or proximal one, remains connected with the apical cell to 
give rise later to successive primary spermatogonia. The cell which is 
separated off (primary spermatogone) is accompanied by one or more 
small nuclei, which later develop into cyst cells. These nuclei 
Munson believes to be derived from very minute granules which occur 
in the peripheral cytoplasm of the apical cell. They are apparently 
the same granules which have been interpreted by other investigators 
as metabolic products. Just why Munson believes the spermatogonia 
to be derived from the apical cell is not apparent, since he admits 
that he has never seen this cell undergoing division, and in all cases 
observed by him it differed greatly in appearance from the sperma- 
togonia. 
Turning now to the other view,— that the apical cell is a support- 
ing or nurse cell,— we find that this interpretation has been accepted 
in some form or other by most authors.. This view was held by 
Ziegler und Vom Rath (91), Toyama (94), Erlanger (96), La Valette 
St. George (’97), Tichomirow (98), Holmgren (:01), Griinberg (:03), 
and recently Cholodkovsky (:05). Holmgren (:01) has traced deeply 
staining granules from the nucleus into the surrounding cytoplasm. 
He also found granules in the cytoplasm of the surrounding spermato- 
