340 



SCIENCE. 



[N. S. Vol. XII. No. 296. 



among the aboriginal tribes of Canada. 

 Professor Cunningham, Dr. Beddoe and 

 Professor A. F. Dixon send papers dealing 

 with questions of anthropometry. 



Professor Sydney H. Vines will preside 

 over the Botanical Section (J). His ad- 

 dress will deal with Botany in the 19th 

 century, and will be a review of the more 

 important advances made in the different 

 departments of the science. As has already 

 been stated, this Section will have a joint 

 discussion with the Geological Section on 

 the Coal Period Vegetation. A museum is 

 being arranged to illustrate the Yorkshire 

 Coal Measure Flora, etc., in connection with 

 the discussion. Mr. Percy Groom, of Coop- 

 ers Hill Engineering College, is to deliver a 

 semi-popular lecture before the Section en- 

 titled ' Plant- form in Relation to Nutrition.' 

 There will also be papers on Fossil Plants, 

 Plant Anatomy, Plant Physiology, etc. 



The Friday evening discourse will be de- 

 livered by Professor Gotch, the subject be- 

 ing Animal Electricity, while that on Mon- 

 day evening will be by Professor "W. Stroud, 

 whose subject will be 'Eange Finders.' 

 Professor Sylvan us P. Thompson will give 

 the lecture to the operative classes on Sat- 

 urday, and will take as his subject ' Elec- 

 tricity in the Industries.' 



VARIATION AMONG SYDBOMEDUS^.* 

 The announcement of Bateson in his 

 ' Materials for the Study of Variation ' that 

 medusEe best illustrated the principle which 

 he designated as ' Discontinuity of Meristic 

 Variation ' led me, in connection with re- 

 searches which have been under way for sev- 

 eral years, to note more specially any indica- 

 tions which might either confirm or discredit 

 this statement. Accordingly I have from 

 time to time m_ade such collections of the 

 Hydromedusse as might afiford a means of 

 testing the matter. While as yet these 

 * Abstract of a paper presented before the Section 

 of Zoology of the American Association. 



have not been extensive, except in a few 

 genera, they seem to be sufficient to war- 

 rant a brief summary Of facts bearing upon 

 the general problem of variation. The 

 collections have been chiefly of the follow- 

 ing genera : Eucope, Obelia, Margelis, Pen- 

 naria and Gonionemus. 



The facts exhibited by Eucope have re- 

 cently been published by Agassiz and Wood- 

 worth, and while I have made observations 

 upon those which I had collected in larger 

 numbers than any other, they are yet so 

 similar to those made by these observers that 

 I shall make no particular reference to them 

 at this time. Of the species of Obelia and 

 Margelis I have as yet had no opportunity 

 for extended study. Facts presented here 

 will have reference only to the species of 

 Pennaria and Gonionemus. 



Of Pennaria the medusse are very small 

 and of a shape which renders rather diffi- 

 cult an examination of the radial canals, a 

 feature which, in my observations, has been 

 among the most variable of structural char- 

 acters. From the examination of only 

 about a hundred specimens I have found 

 no marked variation of this feature except 

 in the direction of atrophy. The medusa 

 of Pennaria seems to be in a somewhat 

 degenerate condition. In many specimens 

 the marginal canal is wholly atrophied and 

 in some cases also the radials, to a greater 

 or less extent. I have elsewhere* pointed 

 out that in many cases the medusfe of this 

 species never become free, but discharge the 

 generative products while remaining con- 

 nected with the polyp. Another feature 

 which may prove to be a variation is the 

 appearance of small wart-like or vesicu- 

 lar protuberances at various points of the 

 exumbrella. Agassiz, in the North American 

 Aealephce, refers to a similar feature but ex- 

 plains it as probably due to the distortion 

 caused by ova in the subumbrellar cavity. 

 This, however, I am strongly convinced is 

 *Am. Nat., May, 1900. 



