318 SCIENCE PROGRESS. 



( i ) The co-existence of two substances at least, nuclein 

 and cytoplasm, is requisite for life. (This is an inference, 

 strictly speaking, and not a fact ; but I think that it may be 

 considered a legitimate inference from what we know of the 

 structure of the lowest bionts, and from the experiments of 

 Nussbaum, Gruber, Verworn and others.) 



(2) The existence of bionts, such as Bacteria, in which 

 we are unable to distinguish more than these two sub- 

 stances. (This is a fact, which lends material support to 

 the above inference.) 



(3) The existence of bionts in which nuclein and cyto- 

 plasm are not indefinitely intermingled, but the former is 

 segregated in the form of particles scattered through the 

 protoplasm, e.g., Trachelocerca phcenicopterus and Chcenia 

 teres. (We gather from this fact that the two chemical 

 substances tend to become separated from one another.) 



(4) The temporary aggregation of nuclein particles to 

 form a centralised nucleus for the purpose of the repro- 

 ductive act, e.g., Holosticha scutellwm. (We infer from this 

 that there is some connection, at present hidden from us, 

 between the nucleus and the reproductive act.) 



(5) The existence of many bionts in which the nuclein 

 is concentrated to form a nucleus. (We infer that this 

 is a grade of permanent differentiation arising out of 

 the previous temporary grade.) 



(6) The existence of many nuclei in all bionts which, 

 whilst still undivided as regards their cytoplasm, attain to a 

 certain size. (From this we infer that the " limit of nuclear 

 influence " cannot extend through a large mass of cyto- 

 plasm.) 



(7) The origin of "cellular" tissues from a ccenocytial 

 mass, e.g., the endosperm of Phanerogams; the neural 

 crest of certain Vertebrate embryoes ; the embryoes of 

 Arthropods; the mesoblast of many Vertebrates, etc. (From 

 this we infer that the cells composing many tissues of higher 

 animals are not to be regarded as bionts, but are secondarily 

 derived during the growth and extension of the parts of a 

 single biont.) 



This re'sume suffices I think to show that this at least 



