254 Mottier. — Development of the Spermatozoid in Char a. 
EXPLANATION OF FIGURES IN PLATE XVII. 
Illustrating Professor Mottier’s paper on the Spermatozoid of Chara. 
All figures were drawn with the aid of the camera lucida and with Zeiss apochromatic homo- 
geneous immersion 2 mm., apert. 1-40 with compensating ocular 8. All are magnified about 2,000 
diameters. 
Fig. 1. Sporogenous cell seen from the end at the beginning of the development of the 
spermatozoid. The blepharoplast appears as a heavier line at the surface of the protoplast above 
and below the nucleus ; the anterior end being on the side below the nucleus. 
Fig. 2. Two spermogenous cells in about the same stage of development as Fig. 1, seen from 
the side, or in longitudinal section. The blepharoplast is seen along the lower transverse wall in 
each cell. The cytoplasm has accumulated into a denser mass along the side next the blepharoplast. 
Fig. 3. A median longitudinal section of a cell in the same stage as Fig. 2, passing through 
the cell in the plane a-b of Fig. 1. The blepharoplast is, therefore, not visible. 
Figs. 4, 5. Later stages in the development as seen from the end. The blepharoplast is well 
differentiated and extends almost or quite around the nucleus. The posterior end, which is on the 
upper side in the figure, is seen to be much broader than the anterior end ; its extremity projects as 
a beak beyond the surface of the protoplast. The anterior end is a very delicate thread curved or 
hooked at its extremity. In Fig. 5, the blepharoplast is separated from the nucleus, probably on 
account of shrinkage, and it is seen to be a continuous thread. The cilia are present at this stage. 
Figs. 6, 7. Similar to the preceding. Fig. 6 shows the mode of attachment of the cilia ; in 
Fig. 7 only a part of one cilium is shown. 
Fig. 8. A later stage. The spermatozoid has begun to assume its characteristic spiral form. 
The ends of the blepharoplast do not lie in the same plane, and were drawn by changing the focus. 
The nucleus is now in the form of a half moon or crescent, and the cytoplasm is correspondingly 
concave. The cilia lie in contact for a part of their length. 
Fig. 9. A later stage than Fig. 8. The nucleus has become sausage-shaped. The granular 
cytoplasm is embraced by the middle portion of the sperm. 
Fig. 10 a and b. Optical longitudinal sections of two cells in about the stage of Fig. 9. a is 
a surface view, and b an optical section. The dark dots in the cells on the right and left of the 
sperm represent sections of the cilia. In b the cytoplasm is concave at the right to correspond to the 
concave side of the sperm. The two crescents seen in this concavity are the transverse sections of 
the ends of the blepharoplast, that of the posterior end being above. These ^sections show that the 
blepharoplast is a convexo-concave band. At the left of the nucleus is seen a section of the blepharo- 
plast closely applied to the nuclear membrane. 
Figs. 11, 12, 13. Successively older stages. The sperm has now become spirally coiled by the 
growth or extension in length of both nucleus and blepharoplast. The cytoplasmic vesicle adhering 
chiefly to the nuclear portion is being gradually diminished. 
Fig. 14. A nearly ripe spermatozoid. The spermatozoids are usually more closely coiled up 
than this one. The granular cytoplasm is more reduced. 
