OF FERNS FROM THEIR SPORES. 123 



their former position so as to render the existence of the enveloping cell or cells very 

 evident. After the whole of the contents have been discharged, the walls of the parent- 

 cell acquire a deep brown colour, presenting a peculiar appearance and making the anato- 

 mical structure of the antheridium very clear (figs. 48, 49). The lower faces of full-grown 

 prothallia exhibit, when moderately magnified, a great number of circular bodies with 

 brown roundish or squarish central patches ; these are effete antheridia, with the brown 

 walls of their cavities showing through the orifice at the summit (see figs. 19 & 50). 



We have next to consider the appearance of the spermatozoids, produced by the sperm- 

 cells. These cells, as stated already, generally emerge entire from the antheridium, the 

 spiral fibre being visible, in movement, in their interior. After a variable time, according 

 to the stage of development of the spermatozoid, it breaks through the wall of the sperm- 

 cell, and if perfect, escapes entirely from it. When perfect it appears to consist of a flat- 

 tened band, curled spirally into about three and a half coils, bearing all along the outer 

 edge, cilia of considerable length, vibrating with great rapidity ; so much so, indeed, that 

 they appear only like a fringe of light while the spermatozoid is in active motion (fig. 40). 

 The filament when in the condition of the lowest specimen in the group (fig. 40) mea- 

 sures about xwoth of an inch in length, as coiled up ; the diameter of the widest coil, 

 about equal to that of the sperm-cell, is usually about -^ooth of an inch. I never saw one 

 uncoiled and flaccid but once ; this measured about 20 3 00 ths of an inch in length (fig. 42 a). 

 The motion consists of a rapid rotation around its axis, which, from the spiral form, causes 

 a motion of great velocity, forwards, in the water. The motion does not seem to follow 

 any fixed rules ; the spermatozoids dart here and there, turn aside or backwards, or alter- 

 nately to the right and left in their course onward, so as to preclude the possibility of laying 

 down any formula or law for it. If they come in contact by the smaller extremity with 

 any fixed body, they often adhere by this point and then revolve around their axes without 

 advancing. By degrees the motion becomes slackened and the rotation is lost, merely a 

 kind of vibratory motion remains, and this at length ceases ; but the spermatozoids seem 

 to undergo dissolution during this time, and when they come to rest often appear as 

 shapeless masses. By applying iodine the movement of the most active can be stopped 

 instantaneously, and in this way a tolerably clear view of the structure is obtained. 

 Under these circumstances the cilia may be seen pretty clearly (fig. 41) ; the flattened 

 band exhibits minute granules adhering to it, and is seen to have a little rounded head, 

 from which the coils run back, increasing successively in diameter, so as to give a conical 

 form to the outline of the whole, as seen at the side. 



Such, so far as I can make it out, is the character of a perfect spermatozoid. But these 

 bodies acquire the capability of motion, of whatever nature this may be, before they are 

 perfectly developed, and hence, I imagine, the different accounts which different observers 

 have given of them. It seemed to me that when they had not acquired their full develop- 

 ment, the fibres could not unroll into the true form when they emerged from the sperm- 

 cell ; they thus appeared to present fewer coils, often only one and a half, the latter of 

 very large diameter ; in other cases they looked like minute shells of Gasteropodous Mol- 

 lusks. In fig. 46 I have given representations of several of these forms, and it should be 

 observed that these imperfect forms exhibited a greater quantity of adherent granules, and 



