784 REPORT— 1900. 



FRIDAY, SEPTEMBER 7. 



The following Papers were read : — 



1. The Miocene Fauna of Patagonia. By Professor W. B. ScoT'i'. 



2. The Nesting Habits of Ornithorhynchus. Bij Dr. Gregg Wilson. 



3. Malaria and Mosquitoes. By Major Ronald Ross. 



4. The Nuclei of Dendrocometes. 

 By Professor S. J. HiCKSON, 3I.A., D.Sc, F.R.S. 



Plate denied the existence of true ' Nehenkerne,' or micron uclei, in Dendro- 

 cometes, and Schneider was unable to prove their existence. There can be no 

 doubt, however, that such bodies do occur, and I have been able by the improved 

 methods of preservation and staining to trace all the important stages of their 

 mitosis. Maupas asserted that in the Suctoria there is only one micronucleus, and 

 that it is very smnll. If this is true of the Suctoria generally, Dendrocometes is 

 exceptional, as there is reason for believing that at least two and sometimes three 

 or four micronuclei occur, each of which is as large as or larger than the micronuclei 

 of Parmnoecium, caudatmn. During conjugation one micronucleus from each 

 individual passes down the connecting bar, and there can be no doubt that a 

 fusion of micronuclei occurs, although the whole series of stages of this process 

 has not yet been observed. 



The macronuclei of the conjugating individuals are very much elongated and 

 pointed at their extremities. In several cases I have observed that one end of the 

 macronucleus of each conjugating individual passes down the connecting bar, and 

 in one specimen an actual fusion of the two macronuclei was seen. 



It would be premature to discuss the meaning of this conjugation of the 

 macronuclei at present, but there can be no doubt of the bearing of this fact upon 

 the prevalent view that the conjugation of Infusoria is entirely an affair of 

 micronuclei. At the end of conjugation the macronucleus disintegrates, as in the 

 Ciliata. The new macronucleus, which makes its appearance during the early 

 stages of the disintegration of the old macronucleus, is at first clear, homogeneous, 

 and almost devoid of chromatin. The chromatin accumulates in it as the frag- 

 ments of the old macronucleus disintegrate. 



The structure of the macronucleus has been very carefully reinvestigated. 

 Details of the results will be published later, but it may be stated here that the 

 division of the macronucleus during gemmation is purely amitotic. There are no 

 centrosomes and no achromatic spindle. 



In this investigation I have been very materially assisted by Mr. T. J. 

 Wadsworth, of the Owens College laboratory. 



The iron haematoxylin method of staining has been principally used, but 

 valuable results have also been obtained by a new method of using brazilin with 

 iron-alum. 



5. Cycloina in Osseous Fishes. By James F. Gemmill, M.A., M.D. 



In this paper an outline is given of the anatomy of some cyclopean trout 

 embi-yos ; the conditions present are contrasted with those which are found in 

 similar cases among the higher animals, and their general bearing is briefly discussed. 



Summary of Chief Points relating to Cyclopia in the Trout. 



1. In all the specimens examined dLstincfc olfactory organs and nerves of 

 reduced size are present. 



