I 50 LOUISE B. WALLACE. 



find the division of the accessory chromosomes in the second 

 maturation mitosis and in the second place I failed to find the 

 tail of the spermatozoon. These points have been fully discussed 

 in the body of this paper. 



Although I am fully aware that it is easy to read one's own 

 interpretation into the work of others, nevertheless I am confident 

 that the spermatogenesis of at least three genera of spiders 

 Agalcna, Epeira and Lycosa will be found to agree in all 

 essential points. 



SUMMARY. 



1. In the spermatogonia the nuclei are unusually large. The 

 chromosomes are rod-like and are probably at least fifty-two in 

 number. Two of them appear different from the others and are 

 regarded as the accessory chromosomes. 



2. In the primary spermatocytes, the ordinary chromosomes 

 conjugate end to end in synapsis to form V-shaped chromosomes 

 These open out along the line of the longitudinal split of the 

 spireme to form double V's and divide reductionally. In the 

 early rest stage the two accessory chromosomes take the form 

 of two chromatin nucleoli which later unite into a single chro- 

 matin nucleolus. At the beginning of the growth period they 

 again take the form of two rods which later conjugate side to side 

 during a small fraction of the growth period. In mitosis they 

 pass over bodily into but one of the two daughter cells. 



3. In the second spermatocytic division the V-shaped chromo- 

 somes and also the two rod-like accessory chromosomes divide 

 equationally. The reduced number of the ordinary chromosomes 

 is probably at least twenty-five. 



4. The spermatozoon has a well-developed axial filament de- 

 rived from the distal centrosome. The proximal centrosome 

 gives rise to the end-knob. 



5. There is dimorphism of the spermatozoa, half of them con- 

 taining two accessory chromosomes and half of them lacking 

 these elements. 



6. Since the accessory chromosomes are more conspicuous 

 during the growth period of the primary spermatocytes than at 

 any other time and in the primary oocytes no trace of them can 

 be found and since the dimorphism of the spermatozoa is due to 



