Mottier. — Development of the Spermatozoid in Char a. 247 
ventral side of the cell. The cilia are fastened to its anterior end. From 
this time onwards the point of insertion of the cilia is unchanged, so that 
the further growth of the thread leads to the formation of that part of 
the sperm anterior to the point of insertion of the cilia. The trans- 
formation taking place in the nucleus during the development, as described 
by Belajefif for Char a foetida , differs in no important detail from my 
own observations on Chara fragilis , a detailed account of which is 
to follow. 
From the foregoing it will be seen that, according to Belajeff, the 
cilia arise from a cytoplasmic protuberance or knob (Hocker), lying near 
the nucleus at the side which is to become the convex side of the mature 
spermatozoid. The formation of a cytoplasmic thread now carries the 
cilia-bearing protuberance some distance from the nucleus, and constitutes 
the anterior cytoplasmic part of the sperm. At the same time a similar, 
though somewhat broader, thread or band develops from the opposite side 
of the nucleus. This constitutes the posterior end of the spermatozoid. 
Judging from Belajeff’s figures these cytoplasmic extremities of the sperm 
seem to be direct transformations of the plasma-membrane (Hautschicht), 
although he does not make a direct statement to that effect. He leaves 
the impression also that the two ends of the sperm are separate pieces, 
being fastened to the respective ends of the nuclear portion. 
Belajeff’s study was made on material stained and observed in toto 
after mounting in glycerine — a method that cannot be regarded at present 
as altogether reliable, yet more improved methods show that many of 
the finer details were brought out with remarkable accuracy. In my 
own study Chara fragilis was used exclusively. The material was fixed 
in chrom-osmic-acetic acid, embedded in paraffin, sectioned and stained 
on the slide with aniline-safranin, gentian-violet and orange G. For 
the most part the sections were cut from three to five microns in 
thickness, but in order to bring whole cells into observation thicker 
sections were prepared. 
Of all the plants below the Ferns, the Characeae are probably the 
most suitable objects for the study of spermatogenesis. The mature 
spermatozoids are relatively large, and the protoplasmic structures of 
their mother-cells can be fairly well differentiated by present cytological 
methods. Yet even here, as in the most favourable cases, there are 
phases in the process which present extreme difficulties, and consequently 
there are points concerning which there is always more or less doubt. 
This I have found true in some of the earlier stages in which cytoplasmic 
differentiation begins. 
As is well known, the spermogenous cells of Chara are arranged in 
long filaments coiled up in the globular antheridium. The cells are in 
the form of flat, cylindrical disks, two or three times as broad as long 
S 
