TBANSACTIONS OF SECTIOX D. 619 



dilute solution of Kleinenberg's hsematoxyline, exhibit a very distinct nuclear 

 structure. 



The division of the nucleus takes place by a process of karyokinesis, comparable 

 to that which takes place in the division of the nucleus in the higher plants. This 

 can be most satisfactorily observed in the nuclei of the oogonia. 



The nuclei of the oogonium at an early stage in the development of the latter 

 are spherical or slightly oval, vesicular bodies, each of which contains a large mass 

 of chromatin, forming a peripheral layer on its wall. 



All the nuclei of the oogonium divide, and the process of division is accom- 

 panied by changes in the protoplasm, leading to the formation of the oosphere. 

 These changes are more complicated than is generally supposed. 



The protoplasm of the oogonium at an early stage appears to be a homogeneous, 

 granular mass containing numerous nuclei, as described above. 



Numerous vacuoles appear in the centre of the oogonium, causing the greater 

 part of the protoplasm and all the nuclei to be restricted to the periphery, leaving 

 in the centre a space, alxjut equal in size to the future oosphere, containing a small 

 central mass of protoplasm, connected to the parietal layer by protoplasmic strands. 

 At the same time the nuclei swell up, and exhibit a thread-like structure. They 

 become arranged very regularly, and form a single layer in the parietal proto- 

 plasm. 



The chromatic threads next arrange themselves in the equatorial plane of the 

 nucleus, and then divide into two groups of threads, each of which forms a daughter 

 nucleus. 



The daughter nuclei again divide, and then two or perhaps more pass towards 

 the centre of the oogonium, and soon afterwards the cell wall of the oosphere 

 begins to form on the inner side of the parietal layer of protoplasm, leaving this, 

 together with the remainder of the nuclei outside, to form the periplasm. 



From this mass of protoplasm and nuclei both the endosporium and the exo- 

 sporium are formed. 



One or more antheridia are developed in connection with the oogonium. Each 

 contains several nuclei, which divide up in the same manner and at the same time 

 as those in the oogonium. The antheridia send out fertilising tubes, swollen at 

 the ends, which pass to one side of the oosphere, come into close contact with it, 

 and appear to open into it by a small aperture. The passage of a nucleus from the 

 antheridium into the oosphere has not been directly observed, but it is probable 

 that fertilisation does take place, as two nuclei have been seen in the oosphere at 

 about the time when a nucleus or nuclei from the antheridium appear to pass 

 over into the fertilising tube, and at a later stage one nucleus only is seen. 



The nuclei of the mycelium divide in a similar manner to those in the oogonium, 

 but they do not become so large nor exhibit the details so clearly. 



The conidia or zoosporangia contain numerous nuclei, difl'ering in structure 

 from the nuclei in the other parts of the fungus. They consist of a central mass 

 of chromatin, surrounded by a layer of nucleoplasm, with a firm outline. They 

 are spherical or slightly oval bodies, a little larger than the nuclei of the mycelium. 



5. The Antherozoids of Cryptogams. 

 By Alfred W. Bennett, M.A., B.Sc, F.L.S. 



The object of this paper was to bring out the difference between the two modea 

 in which the ciliated fertilising organs of Cryptogams are formed, the first type 

 being that which occurs in Vascular Cryptogams, Muscineoe, and Characere, the 

 second in Algaj (excluding Characea)). 



The essential character of the first type is that the antherozoid is formed from 

 the nucleus only of its mother-cell; the whole of the rest of its protoplasm being 

 consumed in the development of the antherozoid. The vibratile cilia which give 

 to the mature antherozoid its power of rapid movement proceed from a peripheral 

 layer of hyaline protoplasm belonging to the nucleus. In Ferns and other Vas- 

 cular Cryptogams these cilia are very numerous, forming a tuft attached to the 



