The Spermatogenesis of tlie Opossum (Didelpliys virginiana) etc. 
67 
number of mitocliondria in the spermatogonia, wliich also are assumed 
to have a similar nuclear origin. 
The arguments of Morse (1909) repeated by Duesberg (1910) that 
nuclear growtli, particularly growtli of plasraosome and accessory chromo- 
some is incompatible with mitochondrial origin from that source, has 
in reality little force. It seems more reasonable to suppose that during a 
stage of great metabolic activity such as characterizes the actively growing 
nucleus, superabundant chromatin would be most available for mito- 
chondrial formation. 
Henneguy (1904) first described mitocliondria in the primary sper- 
matocyte of Pyrrhocoris apterus, Forficula auricularia and Gryllus cam- 
pestris. Zweiger (1907) confirmcd this finding for Forjicula, The 
Schreiners (1905 — 1908) report chondriosomes in the primary spermato- 
cyte of Myxinoides. Tretjakoff (1905) finds the mitochondria in As- 
caris meg. first in the young spermatid. In Ascaris canis, Marcus (1906) 
describes an expulsion of trophoclrromatin into the protoplasm of the 
primary spermatocyte. Likewise Depdolla (1905) in Lumbricus terrestris 
finds mitochondria first in the primary spermatocytes. Pantel and 
de Sinety (1906) state that they are unable to find mitochondria in the 
spermatogonia of Noloneda glauca, They describe a transitory forma- 
tion of “pseudochromosomes” in the primary spermatocytes. Gross 
(1907) describes the appearance of “pseudochromosomes” (mitochondria) 
in the primary spermatocyte of Pyrrhocoris apterus. In Paludina vivi- 
para and Helix pomatia, Popoff (1907) describes the expulsion of nuclear 
substance during the “boucpiet stage” of the growth period. This chro- 
matin is supposed to form chondriosomes, and its elimination to have 
established equilibrium between the protoplasm and nucleus (i. e. tropho- 
chromatin and idiochromatin; (Kern-plasma-relation hypothesis of 
R. Hertwig). Davis (1908) illustrates mitochondria in the primary 
spermatocytes of certain orthoptera; likewise Büchner (1909); Oettinger 
(1909) describes chondriosomes in the primary spermatocytes of Pachyiu- 
lus varius. 
Expulsion of nuclear chromatin during the growth period of the 
primary oocyte has also been described by Moroff (1909) for certain cope- 
pods, Jörgensen (1910) for certain sponges, and Schaxel (1910) for 
certain ascidians. 
On the contrary Benda (1897 — mouse), Retzius (1909 — rat), 
Regaud (1910 — rat), Duesberg (1907 — 1910 — Blaps, Triton , rat, cat, 
and guinea-pig) and others have described mitochondria in the spermato- 
gonia. and in a number of cases have followed their simple distribution 
5 * 
