274 bulletin: museum of compakative zoology. 



regions of the thread represents different qualities which are to be divided 

 and distributed to the daughter-cells according to some definite law." 

 The ultimate purpose of a spireme, then, according to this view, is lost 

 unless its parts retain their identity ; but it seems impossible to show 

 that this is the case in Haminea. Wilson (:01^ p. 572) finds that in 

 Toxopneustes the chromosomes have diffei-ent origins according as a 

 strong or weak solution of magnesium chloride is used, "the chromo- 

 somes arising in one case from the nucleolus, in the other from the 

 general chromatin reticulum." Similarly E. Hertwig ('99) found that 

 in Actinosphaerium the chromosomes liad a different origin, depending 

 upon whether the animal was well fed or starved. Wilson (:01^, p. 575) 

 concludes his discussion of the double origin of the chromosomes with 

 the following statement : "It may be pointed out finally that the 

 foregoing interpretation, if correct, seems to involve the farther conclu- 

 sion that chromatin, or at least the constituent on which the staining 

 reaction depends, must be regarded as a liquid substance that may be 

 absorbed or given off by an ' achromatic ' basis such as plastin or linin, 

 and thus may flow from one part of the nucleus to another. It seems 

 to me further that the facts observed in the magnesium-eggs are not 

 favorable to the hypothesis of the persistent individuality of the chromo- 

 somes." Delage (:01, p. 347) states that the number of the chromosomes 

 " se retablit par autorcgulation : c'est uue constante cellulaire specifique, 

 et la personnalite des chromosomes n'a rien de reel." 



Van Beneden ('83) was one of the earliest investigators to suggest 

 that the chromatin may give rise to the achromatic network and to the 

 nuclear membrane. He further suggested that the chromatin might pass 

 into a chromatic or a non-chromatic condition, according as it took up or 

 gave off chromophilous substance. Coe ('99) finds in Cerebratulus that 

 the nucleus loses its power of holding haematoxylin as soon as the egg 

 is laid, the chromatin gradually reappearing as mitosis proceeds. Wilson 

 (:01*) has shown that the chromatin may pass through different 

 stages, and that the basis of the chromatin must be regarded as a liquid. 

 Hargitt (:00, :04) finds in Peunaria that after the nucleus breaks 

 down during cleavage, the chromatin may entirely disappear, for at that 

 time there is no chromatin reaction with any of the basic stains. Later, 

 when cleavage is under way, the chromatin is again demonstrable. 



In seeking to explain the source of the chi'omatin in Haminea, it is 

 readily seen that the changes already described lend strong support to 

 the views quoted. We have seen that there are to be distinguished two 

 conditions of the chromatin, — the basichromatin and oxychromatin, — 



