816 REPOET — 1893. 



the tenthredinian type of silk glands, -which is composed of a central epithelial duct, 

 together with several elements containing still intracellular ductules. 



It seems to me that the existence of these two types of structure in organs so 

 undoubtedly homogenetic as the silk glands of insects shows that there is no 

 argument against the homology of the nephridia of the leeches with those of other 

 forms, either lower or higher, in the fact that the cavities of one set are intra- 

 cellular, those of the other intercellular. 



At all events, the chief object of this communication is to show : (1) that 

 cytological and histological diiferences, radical as they may be, must not always 

 be considered as a final objection to the homogenetic relations between homologous 

 organs ; (2) that these ditferences deserve, however, to be taken into consideration, 

 and that some interesting researches might be undertaken in that direction. 



6. On Karyokinesis in the Fungi. By Hakold Wager, F.L.S. 



Numerous observations have been made on nuclear division in the fungi which 

 tend to show that in this group, as in the higher plants, it is indirect. In most 

 cases, however, the observations seem to indicate that the division is very much 

 simpler than in the higher plants. 



Sadebeck and Fisch in Exoascus, and IJartog in Saprolegnia, have described a 

 simple nuclear division in which the chi'oniatic portion of the nucleus divides into 

 two more or less equal parts. The author has described, in Peronospora, the 

 division of the nucleus as taking place byj the production, in the first place, of 

 a number of chromosomes, which divide intlo two groups, each of which becomes 

 a daughter nucleus. The division of the nucjleus in these cases is certainly simpler, 

 so far as the observations at present are con(|erned, than those in the higher plants. 



At the Cardiff" Meeting of the Association, however, the author described the 

 structure of the nucleus, and the process of nuclear division in Agaricus stercorarius, 

 and pointed out that not only had the nucleus p structure closely resembling that 

 of the higher plants, but also that the nuclear division more nearly resembles that 

 of the latter, inasmuch as a distinct equatorial plate and apparent spindle figure 

 were formed. 



More recently Rosen has described nuclear division among the Hymenomycetes 

 in species other than those examined by the author. It wUl be useful to summarise 

 briefly his results. According to him the nucleus possesses a distinct membrane, 

 nucleolus, and homogeneous nuclear thread or threads. In the process of division 

 the thread or threads divide up into a number of short pieces ; then a separation 

 of these into two groups takes place, both nucleolus and nuclear membrane persist- 

 ing. The nucleus then divides into two halves ; the nucleolus disappears, and two 

 new nucleoli appear, one in each nucleus. Rosen concludes therefore that the 

 division is a very simple one, and generalises thus for all the fungi. His results 

 do not agree with the author's described prior to the appearance of his paper, 

 except in the fact that the nucleolus persists for a long time. 



Lister's beautiful observations on division of the nucleus in the Myxomycetes 

 do not support Rosen's generalisation, for according to the former a distinct spindle 

 figure is formed, and the process of division closely resembles that which takes place 

 in the higher plants, except, perhaps, in the longitudinal splitting of the threads, 

 which has not yet been seen, 



Gjurasin has very recently published a paper on nuclear division in the Asci of 

 Peziza vesiculosa, in which he shows that not only is a spindle figure produced, 

 but that even the protoplasmic radiations at the poles of the spindle are visible. 

 He notes here, also, the extraordinary persistence of the nucleolus. 



The observations recently made by the author on certain species of the Agari- 

 cinese, Agaricus {Stropharia) stercoranus and A7nanita muscarius all tend to show 

 that we are dealing with precisely the same changes in the indirect division of the 

 nucleus as in those of the higher plants. The nucleus consists of a membrane, 

 nuclear network, and nucleolus ; the network is composed either of a single thread 

 or more than one : it consists of a ground substance, which stains light blue, in 

 which more deeply stained granules are embedded. The nucleus takes up a con- 



