446 



SCIENCE 



[N. S. Vol. XXXVI. No. 927 



a comparatively few feathers exactly like 

 those of the male in full breeding plumage, 

 the majority resembling, rather, those of the 

 male in summer plumage. 



In each of these cases, then, removal of the 

 ovary has been followed by a greater or less 

 assumption of male characters. 



Further light on the subject may be ex- 

 pected in due course from the birds on which 

 ovariotomy has been performed this season, 

 several already having feathers like those of 

 a normal male. 



H. D. Good ALE 



Station foe Experimental Evolution, 

 Cold Spring Haebob, 

 Long Island 



note on a method of mimicking amceboid 



motion and protoplasmic steeaming 



in the same model' 



The following method of mimicking amoe- 

 boid motion and protoplasmic streaming has 

 been employed by me for class-demonstrations 

 during the past five years. As it is extremely 

 simple and yields results which are very strik- 

 ing and instructive, it appears advisable to 

 communicate it to a wider public. 



It is well known that if particles of camphor 

 be dropped upon the surface of clean water 

 they display energetic movements which are 

 attributed to large and unequally distributed 

 alterations in the superficial tension of the air- 

 water surface at points of contact with the 

 camphor.' It occurred to me, therefore, that 

 if camphor could be incorporated into a fluid 

 immiscible with water, drops of the mixture 

 placed upon water might be expected to dis- 

 play surface deformations resembling those 

 occurring in the formation of pseudopodia. 

 This anticipation proved correct. 



I prepare a ten-per-cent. solution of cam- 

 phor-gum in benzol and then, since drops of 

 this water-white liquid are difiScult to observe 

 upon the surface of water, I color it deeply by 

 the addition of Sudan III or Scharlach K. 



' From the Eudolph Spreckels Physiological 

 Laboratory of the University of California. 



'Van der Mensbrugghe, cited after Eayleigh, 

 Proc. Soy. Soc. London, 47, 1890, p. 64. 



If a drop of this mixture be placed upon the 

 surface of water, violent and extremely rapid 

 deformations of surface are observed. Lengthy 

 and irregular "pseudopodia" are rapidly 

 thrown out and withdrawn. The whole drop 

 exhibits a veritable ecstasy of motion which 

 shortly ceases when a fine incrustation of pre- 

 cipitated camphor has spread over the water. 



By successive additions of some viscous 

 liquid such as olive oil to the mixture the 

 motions of the drops can be rendered slower 

 and slower and more readily followed in de- 

 tail by the eye. When at length a mixture is 

 formed of equal volumes of olive oil and the 

 camphor-benzol solution the formation of 

 " pseudopodia " is no longer observed ; in- 

 stead, we observe a prolonged and energetic 

 streaming movement within the drop which 

 mimics in the closest manner imaginable the 

 phenomenon of protoplasmic streaming. 



In this way the modifying influence of vis- 

 cosity upon the reaction of fluid masses to lo- 

 cal changes in superficial tension can be 

 shown in any desired gradation; it appears 

 probable that a superficial semi-solid pellicle 

 must restrain the movement of the fluid in 

 much the same way as internal friction. 

 Hence, the phenomena of protoplasmic 

 streaming and amoeboid motion are readily 

 traced to the same origin. 



T. Brailsford Eobertson 



Univeesity of Calipoenia 



TSE DUNDEE MEETING OF THE BBITISE 

 ASSOCIATION FOB THE ADVANCE- 

 MENT OF SCIENCE "■ 

 The meeting of the British Association at 

 Dundee which has just come to an end will be 

 remembered as one of the pleasantest and most 

 successful in the annals of the association. It 

 was thought to be impossible to surpass the num- 

 ber of members and associates who attended the 

 last Dundee meeting, just 45 years ago; indeed, 

 it was not expected that so high a figure would be 

 reached. But the number this year — 2,504 — is 

 considerably in excess of the total in 1867, and 

 the support accorded to the association by every 

 one in Dundee, from Lord Provost Urquhart to 

 the humblest citizen, has been most gratifying. 



" From the London Times. 



