OF THE GERM CELLS OF METAZOA. 159 



Peripatus, the former, together with the linin contained in the chromosomes (axial 

 threads), together constitute a single continuous linin spirem in the nucleus. 



Rest stage of the spermatocytes. A rest stage in the growth period preceding the 

 prophases of the maturation mitoses is well marked in Euchistus (Fig. 12 and Figs. 

 95-100 of my preceding paper) ; though I can confirm Paulmier's observation that such 

 a stage does not occur in Anasa. It is characterized by a huge true nucleolus, by a 

 rather diffuse and scattered distribution of the chromatin so that chromosomal boundaries 

 are practically indistinguishable, and by the diffuse arrangement of a great amount of 

 idiozome substance all around the nucleus, so that an idiozome mass with sharp outlines 

 is not present ; the idiozome mass in the synapsis stage (Figs. 4, 5, 8), on the contrary, 

 had a sharp and distinct outline. The bivalent chromatin nucleolus has now become 

 nearly rounded in form, rarely showed a dumbbell shape, so that its component parts are 

 very closely apposed. It lies peripheral, in contact with the nuclear membrane, while the 

 true nucleolus lies nearer the centre of the nucleus. Sometimes a much smaller rounded 

 body, staining like the chromatin nucleolus, is also found in the nucleus, but what its 

 origin is I have not been able to determine, for I have not found it in the spermatogonia, 

 though it might well escape detection there on account of its small size. 



As to the terminology adopted by me in my former paper (1898) for the series of 

 stages of the growth period, which has been criticised by McClung (1900), the term 

 " metaphase " was, I grant, used by me incorrectly, for I used it for the commencement 

 of the anaphase, whereas it is really Strasburger's stage comparable to Flemming's " meta- 

 kinesis." However, the exact use of these terms was explained by me (1898, p. 20). 

 In the stages leading up to the resting spermatocyte I distinguished "early anaphase," 

 " synapsis," " postsynapsis," and " telophase " as easily recognizable stages in the growth 

 period of Euchistus which need to be characterized by terms for purposes of description. 

 McClung (I. c.) considers the appearances of the synapsis stage as artefacts ; it is hardly 

 necessary to reply to this criticism, since in all Metozoa where the spermatogenesis has 

 been carefully examined, with the exception of certain Amphibia, the dense massing of 

 the chromosomes in the synapsis stage has been shown to be a perfectly normal phenome- 

 non. As to my use of "telaphase," Heidenhain's (1894, p. 524) definition is: "Unter 

 dem Namen Telekinesis beschreibe ich gewisse Bevvegungen des Kerns und des Mikrocen- 

 trums, welche gegen das Ende der Mitose hin stattfiuden. . . . Die zugehorigen Stadien 

 der Mitose bezeichne ich als Telophasen." Since Heidenhain employed it for the stage 

 just preceding rest in leucocytes, I was warranted in using it for the stage just before the 

 rest stage in the spermatocytes of Euchistus. It must be borne in mind, in the descrip- 

 tion of the changes of the growth period of the germ cells, that a peculiar stage, the 

 synapsis, occurs, not found elsewhere in mitosis, and that this stage modifies to greater or 



