The Spermatogenesis în Pentatoma up to the Formation of the Spermatid. 'IQ 



the cell body now becomes well warked (Figs. 42-44); and since the 

 complete separation of the daughter cells is ended last of all in the 

 region of the spindle, and the latter lies excentrically, it happens that 

 the constriction first shows itself on the side opposite to the spindle. 

 I have been unable to detect any intermediate corpuscles ("Zwischen- 

 körper") on the central spindle fibres in the equatorial plane, i. e. 

 any formation of a cell plate; but central spindle thickenings might 

 nevertheless be present but be obscured by the covering of connective 

 fibres. 



From about the time of the disappearance of the nuclear membrane 

 up to the dyaster stage, the cytoplasm presents a clear, almost 

 structureless appearance, though a narrow layer of fine granules is 

 frequently found close to the cell membrane. Sometimes an irregular 

 mass of idiozome substance occurs on the sides of the spindle (Fig. 41 

 Id. Z.), showing that the latter substance does not wholly disappear 

 in this mitosis; it never becomes arranged around the centrosomes, and 

 it will be recalled that when the central spindle is first formed the 

 latter wanders out of the idiozome. 



In conclusion, attention may be drawn to the only abnormal mitoses 

 observed. The one (Fig. 22) shows an unusually large spermatogonium 

 in the prophase, with the nuclear membrane still present, and a well 

 marked idiozome close to the nucleus, in it 33 chromosomes were 

 counted ; but the real number of the latter was probaly greater, since 

 only a portion of the nucleus lay in the plane of the section. The 

 other case (Fig. 32) was a cell in the monaster stage, with two spindles 

 and four centrosomes. The figure was seen obliquely from the side 

 (and correspondingly all the centrosomes did not all lie in the same 

 plane, as they have been figured), and about 23 chromosomes could 

 be distinguished. But some chromosomes were covered by others and 

 could not be clearly seen, so that a greater number was probably 

 present. If there were 28 chromosomes in this cell, we could explain 

 this case as one representing the monaster stage of a cell which had 

 contained two nuclei, 28 being the double of the normal number of 

 chromosomes. 



B. The Ist spermatocytes from the anaphase to the rest stage. 



The last division of the spermatogonia produces spermatocytes 

 of the first order, which shall here be termed the 1st spermatocytes; 

 the products of the latter may then be called 2nd spermatocytes, and 

 the cells resulting from the division of the last, are the spermatids : this 



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