4- PROCEEDINGS OF THE NATIONAL MUSEUM vol. 74 



0.15, 0.30, 0.30, 0.36, 0.375, 0.405, 0.45, 0.75, 0.8, 0.90, 1.05, 1.15, 1.2, 1.5, 

 1.575, 1.59, 1.875. For the most part this series shows a uniform 

 increase in size, the three greatest gaps being from 0.45 to 0.75, 1.2 to 

 1.5, and 1.59 to 1.875. 



7. The distance from the head at which the first genital primordia 

 make their appearance. In eighteen specimens of the M. expansa 

 group this point was found to vary between the 150th and the 424th 

 segment, the whole series being as follows, the figures representing 

 the number of the segment from the head: 150, 155, 160, 180, 290, 

 300, 300, 316, 320, 320, 340, 350, 390, 400, 400, 410, 415, 424. There is 

 a discontinuity of the series between 180 and 290, the remainder 

 being very even. 



8. The distance from the head at which the first testes may be seen. 

 Of seventeen specimens of the M. expansa group this was found to 

 vary between the 390th and the 1018th segment, the complete series 

 being as follows, the numbers representing the number of the seg- 

 ments from the head : 390, 495, 672, 690, 697, 700, 710, 712, 720, 750, 

 761, 767, 801, 852, 910, 937, 1018. The variation in this series showed 

 no marked discontinuity. 



9. The number of testes was counted in a few segments of twelve 

 specimens of the M. expansa group, and the greatest variation in any 

 one worm was found to be between the 198 and 260 testes per seg- 

 ment, and the greatest variation within the twelve was found to be 

 between 109 and 296. The average number of testes of each segment 

 in each of twelve specimens of the M. expansa group formed the 

 following series, each number representing the average number of 

 testes to the segment: 120, 124, 147, 200, 202, 211, 215, 229, 240, 247, 

 247, 284. 



The size of the testes also showed considerable variation, the great- 

 est variation observed in one individual worm being between 0.07 

 and 0.15 mm. in diameter, and in the group of twelve worms exam- 

 ined the greatest variation observed was between 0.035 and 0.15 mm. 

 The average diameter in millimeters of the testes in sixteen specimens 

 of the M. expansa group was as follows: 0.040, 0.050, 0.052, 0.055, 

 0.060, 0.065, 0.067, 0.067, 0.075, 0.075, 0.077, 0.085, 0.087, 0.110, O.llU, 

 0.115. 



lOi. The number of interproglottidal glands per segment. Of 

 15 specimens of the M. expansa group in which counts were made, 

 the average number of glands to- the segment was found to vary 

 between 0.5 and 64 glands to the segment. The complete series of 

 counts were as follows, each number representing the average num- 

 ber of glands j)resent to the segment: 0.5, 6, 8, 9, 10, 11, 14, 16, 20, 

 40, 45, 54, 58, 60, 64. The greatest variation observed in one indi- 

 vidual was between no gland and 42 glands, and the greatest varia- 



