SPERMATOGENESIS OF ASCARIS 445 
spermatids of Ascaris by which the size of these cells is greatly 
lessened. Many plastin granules are lost when this cytoplasmic 
lobe is thrown off (fig. 13). Such a reduction in the spermatid 
with the consequent loss of these inclusions has been described 
by Struckmann in Strongylus, by Meves in the guinea-pig, by 
van Korff in Phalangista, by Broman in Myxine, by von Ebner 
in Rana and in certain mammals where he refers to these gran- 
ules, probably, when he speaks of ‘tingierbire Korner.’ Dues- 
berg observed it in the rat and Jordan in the oppossum, while 
Rosenberg reports it occurrence in the Arachnida and Vejdovsky 
in Turbellaria. Faure-Fremiet reports the loss of all of these 
granules in the cytoplasmic lobe thrown off by the spermatid of 
Arion. Professor Montgomery discovered a remarkable case of 
the loss of ‘mitochondria’ in Peripatus. Just before the trans- 
formation of the spermatid into the spermatozoon all the mito- 
chondrial material aggregates into a fairly compact body, and 
this is always included in the cytoplasmic lobe which is thrown 
off, so that the mature sperm never contains any of it. If, then, . 
this material is of such great significance in heredity, it must be 
explained why it is so generally partially or wholly lost by the 
developing spermatozoon, in forms ranging all the way from the 
Turbellaria to mammals. 
The true origin of ‘organ-forming substances’ 
s 
I cannot close this brief discussion of the significance of cyto- 
plasmic inclusions in germ and body cells without referring to 
the work of Conklin on ascidian eggs and larvae. No one has 
traced the heredity of specific larval tissues from definite cyto- 
plasmic inclusions more accurately and continuously than he. In 
the fertilized but unsegmented egg of various ascidians, notably 
Cynthia, Conklin found a constant distribution of pigment in 
the cytoplasm. This marks a definite localization of masses of 
protoplasm. These masses differ potentially from one another, 
as Conklin proved by the fact that he could trace the formation 
or origin of the various germ layers, tissues and organs of the 
larva as cleavage progressed to one or another of these masses, 
