•)! 



274: T. B. ROSSETER ON DREPANIDOTAEMA UNDVLATA (KRABBE). 



nection with the Cestoidae having possibly never advanced beyond 

 a gastrula stage in their development were in the main correct, 

 and this mednsoid formation of the six-hooked brood strengthens 

 that conviction, because the next succeeding stage in their develop- 

 ment from the hexacanth stage is the cystic scolex, Cysticercus ; 

 and from this scolex is produced, in its final host, by strobilation, 

 the mature tapeworm. 



Explanation of Plate 19. 



Figs. 1 and 2. Two different aspects of scolex, x 18. 

 Fig. 3. Young proglottis, showing early formation and position 

 of testes in segment, x 18. 



4. Male genital organs in situ, dorsal, x 18: a, male 

 genital pore ; b, cirrus-pouch and cirrus with serpentine 

 vas-deferens enclosed ; c, coiled and looped exterior 

 vas- deferens ; d, testes with vasa-efferentia. 



5. Ft male genital organs in situ, ventral, x 18 : e, female 



genital pore and vagina ; f, vaginal canal ; g, recep- 



taculum seminalis ; hh, distal and proximal ovaries ; 



i, shell-gland ; j, yelk -gland. 

 ,, 6. Uterine segment with mature egg, x 18. 

 ,, 7. Isolated testis with its vasa-efferentia, x 155. 

 „ 8. Male and female genital pores, with cirrus exserted, x 155. 

 „ 9. Medusiform embryo, or hexacanth stage, x 380. 

 „ 10. Hooks from scolex (Figs. 1 and 2): a, primus; b, 



secundus, x 175. 

 ,, 11. a, Dujardin's Taenia angulata, x 200; b, Krabbe's 



T. undulata, x 261. 

 12. a, Dujardin's T. undulata, X 430; b, Krabbe's T. 



aiKjidata, X 920. 



?> 



i> 



Journ. Quekett Microscopical Club, Ser. 2, Vol. IX., No. 58, April 1906. 



