598 ARTHUR THOMSON. 
Similarly Minot has drawn a parallel between the basal, 
according to him, female portion of a spermatoblast and the 
ovum minus its (male) polar cells, which would thus be phy- 
siclogically analogous tosperms. On the other hand, according 
to Weismann, the parallel would be between the surplus 
“ ovogenetic” polar vesicles and the surplus spermatogenetic 
basal protoplasm and nucleus, between the preponderatingly 
germinal nucleus of the ovum and the combined nuclei of the 
spermatocytes. It is, however, impossible to decide as to these 
parallels until, on the one band, some method be discovered 
for demonstrating the physiological similarities of protoplasmic 
masses, and, on the other, the exact behaviour of the nuclei in 
spermatogenesis be more satisfactorily known. The cell or cy- 
tophore in the centre of a mass of spermatocytes has also been 
regarded as a separated-off portion of the spermatogonium, and 
physiologically compared with polar cells, but Voigt (‘ Arb.,” 
Wiirzburg, viii, 85) has recently emphatically denied'its cellular 
nature, and ascribed its origin to the stalk of the spermatego- 
nium cell, which, as the latter divides, comes to lie in the midst 
of the spermatocytes. In spermatocytes a peculiar body, first 
described by La Valette St. George (Nebenkern), has been 
lately the subject of much discussion, some deriving it from 
the protoplasm and others from the nucleus, some regarding it 
as separated from the formation of the spermatozoon, and 
others regarding it as the origin of the sperm cap, or middle 
portion or even head. 
Morphological Import of Polar Cells—tThe per- 
sistence of such a process as polar cell-formation seems to point 
to a morphological import, and it is on this aspect of the phe- 
nomenon that most recent investigators have concentrated 
their attention. 
The definite cellular nature of the extruded bodies, which is 
generally acknowledged, the definiteness of their mode of 
formation, their occasional subsequent division, and the preva- 
lence of their occurrence, point, however, to a distinct mor- 
phological import, and that, as Weismann emphasises, of ancient 
phylogenetic origin, which has of course again to be explained in 
