SPERMATOZOEDS. 327 



dition of dense saline and other solutions. All of the alka- 

 line animal fluids of moderate viscidity favor the movements, 

 while the action of acid or of very dilute solutions is unfa- 

 vorable. The movements are suspended by extreme cold, but 

 return when the ordinary temperature is restored. 1 



Before the age of puberty, the seminiferous tubes are 

 much smaller than in the adult, and contain small, trans- 

 parent cells, which, in their form and arrangement, resemble 

 epithelium. As puberty approaches, however, the tubes be- 

 come larger, and the cell-contents increase in size. At this 

 time, there seem to be two kinds of cells ; an epithelium, 

 in the form of irregularly-shaped cells, lining the tubes, and 

 rounded cells, containing one or more nuclei, some of the 

 cells appearing to be in process of segmentation. Many of 

 the cells lining the tube, according to La Valette St. George, 

 present a rounded portion, with a large, clear nucleus, applied 

 to the tube-wall, each with a caudate prolongation projecting 

 into the tube. 2 Sometimes the projections from the different 

 cells anastomose with each other, forming a kind of net- 

 work, which is possibly the appearance of segmentation, de- 

 scribed by Kolliker. 



In the central portions of the tubes of the adult, are 

 rounded vesicles, from -g^W to -g^ of an inch in diameter, 

 each containing from two to twenty transparent nuclei 

 measuring from 50 * QO to -g-^or of an inch. In these, which 

 are called the seminal cells, La Yalette St. George has dis- 

 covered amoeboid movements. 3 The large vesicles with mul- 

 tiple nuclei are the seat of development of the spermato- 

 zoids. The nuclei of the vesicles appear to be transformed 

 into the heads of the spermatozoids, and the filamentous ap- 

 pendages, which are seen in the vesicles in various stages of 

 formation, are developed gradually. It often occurs that, 



1 KOLLIKER, Elements tfhistologie humaine, Paris, 1868, p. 683. 

 * LA VALETTE ST. GEORGE, in STRICKER, Manual of Human and Comparative 

 Histology, The New Sydenham Society, London, 1872, vol. ii., p. 138. 

 3 Op. tit., p. 141. 



