344 THOS. H. MONTGOMERY, 



cell the so-called "nuclear reticulum". In most nuclei of Metazoa, if 

 not in all, this is made up of two distinct elements: 1) the linin 

 (so-called achromatic) network, along or in which is found 2) the 

 chromatin. Whether there is more than one substance included under 

 ï'lemming's terra „chromatin" need not be discussed here. The point 

 of importance for the present consideration is that the chromatin 

 whether in the form of threads, minute granules, or larger masses, 

 appears always (in the Metazoan nuclei which have been carefully 

 studied) to be connected with linin threads or fibrils, and never to 

 be freely suspended in the caryolymph without linin connections. In 

 rest and in mitosis, wherever there is chromatin there would seem to 

 be linin connected with it. Besides the linin which thus forms the 

 supporting portion of the nuclear reticulum, there are found also 

 achromatic fibres which may connect chromatin granules with the 

 nuclear membrane, or which may form delicate networks in the nuc- 

 lear sap (as shown by Heidenhain, 1892; Heidenhain describes the 

 lanthanin granules as distributed along these fibres). Whether such 

 achromatic structures are morphologically and chemically similar to 

 linin of the nuclear reticulum, is, I think, by no means determined; 

 in my description I have called them "secondary linin fibrils" for 

 convenience in distinguishing them from the other achromatic threads. 



Though this relation of the chromatin and linin seems to be 

 well proved for Metazoan nuclei in general, yet frequently there is a 

 loose use made of the term "nuclear reticulum", a use which would 

 imply that it might consist simply of chromatin. Such loose usage is to 

 be deplored, for it tends to obscure the clear concept of the spatial 

 relations of chromatin and linin. 



In the state of union of chromatin and linin which is called a 

 "chromosome" (Waldeyer, 1888) the chromatin granules are more 

 densely concentrated than in other stages, but linin connections of 

 the granules still continue, and form the matrices of the chromosomes. 

 When the nucleus passes into the rest stage the chromatin granules 

 separate more widely from one another, but their linin connections 

 still remain. Now it is the continuance of these linin connections 

 which affords a basis for understanding the movements of the chro- 

 matin and which I think puts into a somewhat new light the concept 

 "chromosome". First let us briefly review the observations on 

 the spermatogenesis of Peripatus, in so far as they bear upon this 

 point; these results are shown concisely in the diagrams 257 — 261, 

 Plate 25. 



