2 28 BIOLOGICAL LECTURES. 



tin. This practically restates Boveri's archoplasm theory as he 

 gave it out twelve years ago — a theory which has been virtually 

 unaccepted so far as the structures for which it was developed 

 are concerned, but which finds its greatest support in the Pro- 

 tozoa. Originally cytoplasmic, this substance, after taking the 

 form of a definite kinetic body, became intranuclear during 

 division of the cell — a condition which is permanent in the 

 majority of the Protozoa, and which is repeated, during mitosis, 

 by every cell throughout the animal and plant kingdoms. 



Within the nucleus the archoplasm body, at first definite 

 and compact (Flagellata), became secondarily diffuse, appearing 

 indefinite in structure {Amoeba proteiis) or evenly distributed as 

 linin throughout the nucleus {ActinospJim'ium, EtiglypJia, Acti- 

 nophrys, and nuclei of higher animals and plants), while, during 

 division, it now re-collects to form the pole plates {Infusoria 

 and many Sarcodina), or spindle fibers and "archoplasm" 

 (Metazoa). 



The origin of the extranuclear sphere may be interpreted in 

 two possible ways. It may be regarded as a direct continua- 

 tion of the primitive cytoplasmic condition through forms like 

 Tetramitiis, Paranicsba, and Noctiluca, where it never becomes 

 intranuclear more than the central spindle does in the latter 

 form ; or it may be regarded as nuclear in origin, being sec- 

 ondarily extruded from the nucleus, as Hertwig describes in the 

 case of ActijiospJicBrinm, or Schaudinn in the case of AcantJio- 

 cystis. In the former case both Brauer and Hertwig are agreed 

 that the cytoplasmic mass {Kegel) comes from the achromatic 

 substance of the nucleus, hence from the intranuclear archo- 

 plasm, and as this substance becomes the matrix for the later 

 appearing centrosomes, it is not incorrect to speak of it as the 

 sphere. 



Whatever its primitive relation to the nucleus may have been, 

 the cytoplasmic sphere is large and permanent in Noctiluca, but 

 it becomes smaller in Metazoa; and just as it becomes diffused 

 throughout the nucleus in Protozoa and Metazoa, so it may be- 

 come diffused throughout the cytoplasm in Metazoa — a condition 

 which Boveri postulated in his remodeling of the archoplasm 

 theory ('95). In higher plants, also, it may be regarded as per- 



