124 MR. HENFREY ON THE DEVELOPMENT 



a less definite outline than the others. Finally, some appeared unable to extricate them- 

 selves from the sperm-cell, and carried this along attached to the posterior extremity 

 (fig. 44). This vesicle attached to the spermatozoid has been described by some observers 

 as formed by the swelling of the extremity of the filament after its exit from the sperm- 

 cells, therefore as constituting an integral part of the structure of the spermatozoid ; but 

 I believe this to be an error. 



In one case I saw an appearance which seemed to indicate the existence of a hair-like 

 production of the posterior extremity of the spermatozoid, like that figured by Hofmeister. 

 A spermatozoid moving rapidly forwards in the water dragged after it, at a little distance, 

 a small mass of mucilage (fig. 42 b) ; the bond of connection was invisible, and therefore, 

 most probably, must have consisted of a capillary process. I never saw any hair-like tail 

 in specimens suddenly paralysed by iodine, but it may have escaped notice from its 

 tenuity ; on the other hand, it may possibly be only found in the most perfect state of the 

 spermatozoid, and since these are examined under artificial conditions, often causing the 

 rupture of the antheridia before their contents are mature, the most perfect condition may 

 only be met with occasionally. 



III. The Archegonitjm. 



In the description of the development of the prothallium, it has been stated that a 

 thickened, cushion-like mass is formed in the central region, by the time the general form 

 has become complete (fig. 51). This central mass is composed of several layers of cells, 

 and, projecting from the general surface, does not reach quite to the inner extremity of the 

 anterior notch of the prothallium, so that an inclined surface is produced looking somewhat 

 forwards toward the notch (fig. 52). Upon this arise the archegonia, which are variable 

 in number, seldom however exceeding six or eight. 



The earliest rudiment of the archegonmm is the embryo-sac, as it may be termed, con- 

 sisting of one of the cells of the thickened cushion, separated by a single cell from the 

 (inferior) surface of the prothallium (figs. 54 — 57 a). A cell, destined to become an embryo- 

 sac, is found surrounded by a circle of cells of smaller size than those of the surroundi 

 tissue, and formed by the production of walls in the cells immediately bordering the 

 embryo-sac, tangental to the circumference of the latter, which thus becomes defined by 

 wall of small cells surrounding it (figs. 55, 57 b). Cell-division also takes place in the 

 cells beneath the embryo-sac, and these multiply so as to form a collection of condensed 

 tissue enclosing the embryo-sac at the sides and below (figs. 66, 67 b), visible through the 

 cells of the surface of the prothallium (figs. 54, 56) before the external structure is formed. 

 The commencement of the development of this consists in the enlargement of the cell sepa- 

 rating the embryo-sac from the surface, and its division into two cells by an inclined wall, 

 the larger of these being again divided by another partition at right angles to the former, 

 so that as seen from the (under) face of the prothallium (fig. 52), the superficial cell seems 

 divided into three. I could not follow the development of the cells, step by step, onwarc 

 from this point, but it is evident that they go on repeating the mode of subdivision of the 

 first cell ; that is to say, the process is as follows : the original cell, A, divides by an oblique 

 septum into an upper, b, and lower, a, the latter being divided by a radial septum intc 



