96 C. M. CHILD. 



have been observed and in one of the turbellaria, a form with much 

 larger nuclei, I have recently seen something similar and am there- 

 fore inclined to believe that cases of this sort actually do occur. 

 In later stages the old membrane seems to disappear leaving two 

 separate nuclei. 



The occurrence of amitosis is probably to be regarded as the 

 result of the establishment of more or less independent functional 

 regions in different parts of the nucleus and the consequent forma- 

 tion of a membrane about each of these. The details of the proc- 

 ess must of course differ according to conditions so that many 

 different forms of amitosis may occur, all due primarily to the 

 same factors. The "endogenous" method of division is not 

 perhaps so widely different from the others as might appear. 

 The old nucleus is so large or the new " functional " nuclei so 

 small that parts of the old nucleus are left out when the new 

 membranes are formed. Ordinarily the new membranes are 

 formed in direct contact, here they are merely formed separately. 



As regards the process of mitosis but little need be said here. 

 The maturation mitoses will be described later but the tissue 

 mitoses and those in the germ mother-cells differ more or less 

 from these. In preparation for mitosis the nucleus stains more 

 deeply and traces of a spireme are sometimes seen but the prepa- 

 ration first becomes readily recognizable when the chromosomes 

 are formed (Fig. 8, A). The largest number of chromosomes 

 counted is fourteen but accuracy is out of the question here. 

 Fig. 8, B, shows a case where twelve were clearly seen. A 

 spindle in metaphase is seen in Fig. 8, A ; it is usually possible 

 to distinguish dark bodies at the poles but much depends on the 

 degree of extraction ; the spindle fibers are very delicate and 

 astral radiations are not certainly distinguishable. A later stage 

 is seen in a, Fig. 5. Any stage of the division from the forma- 

 tion of the chromosomes to and including the late anaphase is as 

 readily recognizable in the sections as in the figures. 



The occurrence of these two forms of division side by side is 

 an indubitable fact, but further data will be given in following 

 papers. There can be little doubt that each form of division is a 

 reaction to special conditions. Certain observations of my own 

 indicate that amitosis occurs more frequently in very rapid and 



