417 



freedom to tliem is of such paiamount importance tliat, for 

 the sake of securing it, a good deal of wildness on the part 

 of weaker brethren may be overlooked. In more senses than 

 one Mr. Darwin has drawn heavily upon the scientific 

 tolerance of his age. He has drawn heavily upon time in 

 his development of species, and he has drawn adventurously 

 upon matter in his theory of pangenesis. According to this 

 theory, a germ already microscopic is a world of minor germs. 

 Not only is the organism as a whole wrapped up in the germ, 

 but every organ of the organism has there its special seed. 

 This, I say, is an adventurous draft on the power of matter 

 to divide itself and distribute its forces. But, unless we are 

 perfectly sure that he is overstepping the bounds of reason, 

 that he is unwittingly sinning against observed fact or de- 

 monstrated law — for a mind like that of Darwin can never 

 sin wittingly against either fact or law — we ought, I think, 

 to be cautious in limiting his intellectual horizon. If there 

 be the least doubt in the matter, it ought to be given in 

 favour of the freedom of such a mind. To it a vast possi- 

 bility is in itself a dynamic power, though the possibility 

 may never be drawn upon. It gives me pleasure to tliink 

 that the facts and reasonings of this discourse tend rather 

 towards the justification of Mr. Darwin than towards his 

 condemnation, that they tend rather to augment than to 

 diminish the cubic space demanded by this soaring specula- 

 tor ; for they seem to show the perfect competence of matter 

 and force, as regards divisibility and distribution, to bear the 

 heaviest strain that he has hitherto imposed upon them. — 

 Professor Tyndall/ Address to the British Association, \d>10, 

 on the Scientific Use of the Imagination.'' 



Migration Theory. — A paper was read on this subject by Dr. 

 Caton at the Biological Section of the British Association. 

 The result of a number of experiments on the mesentery of 

 the frog Avere described, in which the phenomena described 

 by Cohnheim were observed. Inflammation in the fish and 

 tadpole had also been studied ; in the former, congestion was 

 found to be absent during inflammation ; this peculiarity was 

 referred to the venous heart. Though the formation of pus - 

 cells was observed, migration was never seen. In the tadpole, 

 migration was observed to occur very frequently, produced 

 by the slightest congestion, and even when all local irritation 

 had been carefully avoided. The general conclusions arrived 

 at, were that cell-migration depends on congestion, and that 

 its connection with the suppurative process is very doubtful. 

 Cell-migration in the tadpole Avas exhibited under the micro- 

 scope on one of the days of the meeting. 



