n MUSCINE^— HEPATIC^— MARCHANTIALES 31 



has the form of a long-necked flask with a much enlarged base. 

 The canal cells are completely indistinguishable, their walls 

 having become absorbed and the contents run together into a 

 granular mass. The nuclei of the neck-canal cells are small 

 and not readily recognisable after the breaking down of the 

 cell walls, but from analogy with the higher forms it is not 

 likely that they completely disappear in the ripe archegonium. 

 The cytoplasm of the central cell contracts to form the naked 

 globular Qgg. The cytoplasm is filled with granules, and the 

 nucleus, which is of moderate size, shows a distinct nucleolus, 

 but very little chromatin. A special receptive spot was not 

 certainly to be seen. 



Almost coincident with the first cell division in the arche- 

 gonium rudiment there is a rapid growth of the cells imme- 

 diately surrounding it. These grow up as a sort of ring or 

 ridge about the archegonium, which is thus gradually immersed 

 in a cup-shaped cavity, and the growth of the cells about this 

 keeps pace with the increase in length of the archegonium, so 

 that even when fully grown only the very extremity of the 

 neck projects above the level of the thallus. The whole process 

 is undoubtedly but a modification of the ordinary growth of 

 the dorsal part of the thallus, and the space about the arche- 

 gonium is the direct equivalent of the ordinary air-spaces. 



The first division in the primary antheridial cell is the 

 same as in the archegonium, but the later divisions differ much 

 and do not show such absolute uniformity. The first division 

 wall in the upper cell (Fig. 5, B) is always transverse, and 

 this is followed by a second similar wall, but the subsequent 

 divisions show considerable variation even in the same species. 

 After a varying number of transverse walls have been formed, 

 in most cases the next divisions, which are formed only in the 

 middle segments, are vertical, and divide the segments into 

 quadrants of a circle when seen in transverse section. Occa- 

 sionally a case is met with where the division walls are inclined 

 alternately right and left, and the divisions strongly recall 

 those of the typical Moss antheridium (Fig. 5, D). 



The separation of the sperm cells is brought about by a 

 series of periclinal walls in a number of the middle segments, 

 by which four central cells in each segment (Fig. 5, G) are 

 separated from as many peripheral cells. These central cells 



