II MUSCINE^— HEPATIC.^— MARCHANTIACE^ 17 



which sometimes changes into a red or yellow pigment at 

 maturity. The inner cells give rise to a very large number of 

 sperm cells, which in' most Hepaticae are extremely small, and 

 consequently not well adapted to studying the development of 

 the spermatozoids. In a few forms, however, they are larger ; 

 and in Pellia especially, where the sperm cells are relatively 

 large, the development has been carefully studied by Guignard,^ 

 Buchtien," and others of late years, as well as by many of the 

 earlier observers, and a comparison with other Hepaticae 

 shows great uniformity in regard to the origin and development 

 of the spermatozoid. After the last division of the central cells 

 the nuclei retain their flattened form, and thus the sperm cells 

 remain in pairs, an appearance very common in the ripe 

 antheridium of most Liverworts. Just before the differentiation 

 of the body of the spermatozoid begins, the nucleus has the 

 appearance of an ordinary resting nucleus, but no nucleolus 

 can be seen. The first change is an indentation in the edge of 

 the discoid nucleus, and this deepens rapidly until the nucleus 

 assumes a crescent form. One of the ends is somewhat sharper 

 and more slender than the other, and this constitutes the 

 anterior end. As the body of the spermatozoid grows in length 

 it becomes more and more homogeneous, the separate chromo- 

 somes apparently fusing together as the body develops. The 

 body of the spermatozoid increases in length until it forms a 

 slender spiral band coiled in a single plane, lying parallel with 

 the one in its sister cell. 



The full-grown spermatozoid in Pellia epipJiylla has, accord- 

 ing to Guignard,^ from three to four complete coils. Most 

 Hepaticae have much smaller spermatozoids, and they have 

 fewer coils than in Pellia. In all the Hepaticae the spermato- 

 zoid is provided with two cilia, which sometimes exceed in 

 length the body. There is still some disagreement as to 

 their exact method of formation, but from the latest re- 

 searches of Strasburger '^ it seems probable that they arise 

 as direct outgrowths of the forward end of the body of 

 the spermatozoid, this pointed anterior portion not being 

 nuclear in nature, but composed of what Strasburger calls 

 " kinoplasm." They begin to form at an early stage in the 

 development of the spermatozoid, and reach their full length 



^ Guignard (l). ^ Buchtien (i). 



^ Guignard (i), p. 67. ■* Strasburger (8), pt. iv. p. 125. 



