70 CYTOPLASMIC STRUCTURES IN THE SEMINAL EPITHELIUM OF THE OPOSSUM. 



Before undertaking the critique of Schreiner's paper, a few remarks of a general 

 character would seem not to be amiss. Schreiner's assertion of the nuclear origin 

 of his "Plasmafaden" recalls to my mind two other papers in which a similar asser- 

 tion was made: one by Wassilieff (1907) on the seminal cells of Blatta germanica, 

 the other by Jordan on Didelphys. In both cases it was claimed that the chon- 

 driosomes were formed in the spermatocytes only and in both cases I found (a 

 positive result against a negative one) that the chondriosomes were present in the 

 spermatogonia and were transmitted during mitosis to the spermatocytes. For 

 Blatta the formation of chondriosomes at the expense of nuclear material was sup- 

 posed to appear so clearly that Goldschmidt speaks of "die schonen Befunde von 

 Wassilieff, deren unbedingte Beweiskraft fur den, der die Praparate kennt, die 

 noch viel klarer sind als die Zeichnungen, keinem Zweifel unterliegen kann (1909, 

 p. 110)." When, however, I studied the same material (1910), I could find no evi- 

 dence to substantiate the nuclear origin of the chondriosomes and, so far as I am 

 aware, no answer has ever been made to my criticism of Wassilieff's conclusions. 

 In fact, the sharpest critics of Goldschmidt's theory have since been found in his 

 own laboratory, a point to which I shall return later. 



These two experiences, together with the increased knowledge I have acquired 

 of cytoplasmic structures, have made me very skeptical of such claims as Schreiner's. 

 As to the present case, I might add that (like others, who have not forgotten the 

 story of the enumeration of chromosomes in Zoogonus mirus) I am not inclined to 

 accept Schreiner's assertions as "ready money." W T hen one attempts, however, a 

 specific and detailed consideration of his present observations, it readily appears 

 that a thorough discussion is hardly possible, as Schreiner's communication is only 

 a preliminary one, in which he repeatedly refers to his future paper and on points 

 of no minor importance. Let us take for example the question of the seriation of 

 the different aspects of the "Plasmafaden." A priori, there is no reason why we 

 should accept that figure 20 represents a stage of fragmentation of these bodies, 

 while certain granular filaments in figures 4, 5, 6, and 7 represent their formation. 

 A correct seriation is, in fact, very difficult, for in most cells not only smooth fila- 

 ments, but also granular ones, which Schreiner supposes to be here in process of 

 formation, there of fragmentation, are present (see pages 159 and 164). The author 

 himself admits the difficulty; one of his criteria is the condition of the nuclei: 



"Auch der Kern hat in den Zellen, wo die Segmentierung stattfindet, ein von demjenigen 

 ganz verschiedenes Aussehen, das wir von den Zellen kennen, innerhalb deren Cytoplasma 

 die Stabchen gebildet werden. Betreffs dieses letzteren Punktes muss auf meine 

 ausfiihrliche Arbeit verwiesen werden (p. 163)." 



As I have not seen Schreiner's completed paper, I can not express any opinion 

 as to the value of his arguments and will therefore limit myself to pointing out the 

 difficulty. I might state incidentally that there is a contradiction (at least what 

 appears to be a contradiction in the face of available data) between figure 22 (which 

 shows smooth filaments only and a nearly spherical nucleus) and the description on 

 page 160, where we read that "diejenigen Fettzellen, die in ihrem Cytoplasma 

 zahlreiche grosse Ktigelchen enthalten, spharische Kerne mit ebenfalls runden 



