486 MICHAEL F. GUYEß, 



nity are ordinarily not so heavy as the corresponding ones on the 

 opposite side. 



Sexaal development. The first definite appearance of the 

 sexual Organs occurs in the small anterior proglottids measuring 

 0.8 mm long by 0.6 mm wide. 



The first indication seen is a transverse streak about the middle 

 of the proglottid, extending from near the median longitudinal line to 

 within a short distance of the edge, and bearing at the outer end a 

 club-like swelling. The streak is the "Anlage" of the vagina and vas 

 deferens, and the enlarged end will ultimately develop into the 

 sexual pore. The development goes on very rapidly, for in proglot- 

 tids a very short distance further back, the streak has grown to form 

 a quarter circle, the inner end of which extends toward the posterior 

 end of the proglottid. Soon, in proglottids measuring 1.2 mm long 

 by 0.84 mm wide, a sort of a Y is formed with the short arm extend- 

 ing forward. In this stage the largest diameter of the developing 

 Organs is at a point near the edge where the future pore will deve- 

 lope. Here also, the first indications of the differentiation into the 

 vagina and vas deferens are seen, the interraediate substance becom- 

 ing gradually thinned out. In proglottids measuring 1.6 mm long by 

 1.9 mm wide, an almost complete Separation of vas deferens and 

 vagina has taken place. They still, however, remaiu in contact in 

 the deeply staining, club-like portion which is the Anlage of the pore. 

 In this stage the uterus has extended forward as far as it ever does 

 before branchiug, but has not yet attained the width it reaches in 

 the sexually mature proglottids. It bends somewhat out of its course 

 to pass around the end of the vas deferens, and then back at a sharp 

 angle resuming its former course until it finally connects posteriorly 

 with the ending of the vagina, which shows two enlargemeuts in about 

 the region where the receptaculum and shell gland will appear. By 

 this time the joined end of the vagina and vas deferens have reached 

 the lateral edge of the proglottids. 



In proglottids measuring 1.7 mm long by 1.8 mm wide the ovary 

 first makes its appearance, as a granulär bean-shaped area. The 

 testes have also put in appearance and are very little if any older 

 than the ovary. In these proglottids the pore has established its 

 connection with the exterior and the cirrus pouch is formed. The 

 vas deferens has somewhat the appearance of a thread within an outer 

 tube or case. The sheath around the vagina is also discernible. At 



