228 SCIENCE PROGRESS. 



of its weight. Of course it may be objected that the 

 alveolar walls and contents may be composed of biophors 

 so small as to defy detection ; such an objection must be 

 defended on theoretical grounds, and I will deal with it 

 presently ; just now I will confine myself to the considera- 

 tion of the visible structure of protoplasm. 



After rejecting the granular theory we have a choice of 

 several others ; the fibrillar theory, the reticular theory, and 

 the alveolar theory of Biitschli. It would take too long for 

 me to examine these several theories in detail ; it has 

 already been done by Biitschli (loc. ciL, p. 177), and still 

 more recently by Yves Delage, 1 if I were to undertake the 

 task I should only give a resume of their arguments. 

 For my own part I am strongly inclined in favour of Biit- 

 schli's " Wabenlehre ". 



For some reason or other Biitschli's account of the 

 structure of protoplasm has not, to use a common ex- 

 pression, " caught on ". Possibly because it was published 

 at a time when men's minds were occupied with the more 

 alluring prospect offered by the granular theory of proto- 

 plasm, with all its delusive hopes of an explanation by means 

 of biophors, and primary organisation of the phenomena 

 of heredity, and of all the vital processes. Possibly also 

 because Biitschli himself pushed the analogy between micro- 

 scopic foams and protoplasmic structure too far. But if 

 his theoretical considerations are put aside, there is a great 

 deal to be said for his fundamental views. The alveolar 

 structure which he describes may be demonstrated in many 

 various forms of protoplasm. It is particularly obvious in 

 Pelomyxa, in which form the larger vacuoles serve admir- 

 ably as a contrast between the finer alveolar structure which 

 he claims to be common to all protoplasm and the grosser 

 vacuolar structure which is often mistaken for it. I have 

 myself identified the alveolar structure in a considerable 

 variety of protozoa, and in a number of tissue cells, and I 

 have succeeded in making Biitschli's artificial amoebae, and am 



1 Yves Delage, La Structure du Protoplasma et les Theories sur 

 V Heredite et les grands problems de la Biologie generate. Paris : C. 

 Reinevald et Cie, 1895. 



