10(5 
Heligmosomum muris Yokogawa 
Fig. 5. 
Fig. 6. 
Fig. 7. 
PLATE VIII. 
Filariform larva, just before casting of the cuticula in the first moult. 
Mature filariform larva in infective stage. 
Larva in the first parasitic stage, 23 hours after infection in the lung of experimental rat. 
PLATE IX. 
Figs. 8-16 of Plate IX and Figs. 19 and 21 of Plate X show the development of the 
external sex-organs—bursa, spicules, etc.—of the male. 
Fig. 8. Posterior end of male in the first parasitic stage 23 hours after infection. 
Fig. 9. Posterior end of male in the first parasitic stage 30 hours after infection. 
Fig. 10. Posterior end of male in the first parasitic stage 40 hours after infection. 
Fig. 11. Posterior end of male during the second moult 48 hours after infection. 
Fig. 12. Posterior end of male in the beginning of the second parasitic stage, 62 hours after 
infection. 
Fig. 13. Posterior end of male in the second parasitic stage 70 hours after infection. 
Fig. 14. Posterior end of male in the second parasitic stage 80 hours after infection. 
Fig. 15. Posterior end of male in the second parasitic stage 90 hours after infection. 
Figs. 8-15 represent optical sections through the middle of the posterior end of the males. 
Fig. 16. Surface view of posterior end of male in the second parasitic stage 90 hours after infection. 
Fig. 17. A portion of the body of a male, 60 hours after infection, showing the genital primordium 
divided into two distinct parts. 
PLATE X. 
Fig. 18. Male in the second parasitic stage 72 hours after infection. 
Fig. 19. Posterior region of male in the second parasitic stage, 96 hours after infection. 
Fig. 20. A portion of the body of a male, 108 hours after infection, showing the development 
of the vas deferens, seminal vesicle and cement glands. 
Fig. 21. Posterior end of male at the beginning of third parasitic stage 120 hours after infection. 
PLATE XI. 
Figs. 22-31 show the development of the external reproductive organs of the female. 
Fig. 22. Posterior end of female in the first parasitic stage 23 hours after infection. 
Fig. 23. Posterior end of female in the first parasitic stage 35 hours after infection. 
Fig. 24. Posterior end of female during the second moult 48 hours after infection. 
Fig. 25. Posterior end of female at beginning of the second parasitic stage 55 hours after infection. 
Fig. 26. Posterior end of female in the second parasitic stage 60 hours after infection. 
Fig. 27. Posterior end of female in the second parasitic stage 70 hours after infection. 
Fig. 28. Posterior end of female in the second parasitic stage 76 hours after infection. 
Fig. 29. Posterior end of female in the second parasitic stage 85 hours after infection. 
Fig. 30. Posterior end of female during the third moult 100 hours after infection. 
Fig. 31. Posterior end of female at the beginning of the third parasitic stage 120 hours after 
infection. 
PLATE XII. 
Fig. 32. A small portion of the body of a female in the second parasitic stage 82 hours after 
infection showing part of the ovary and seminal receptacle. 
Fig. 33. A portion of the body of a female in the second parasitic stage 120 hours after infection 
showing the formation of the oviduct. 
Fig. 34. A portion of the body of a female in the second parasitic stage 120 hours after infection 
showing the oviduct more advanced in development than in Fig. 33. 
Fig. 35. A portion of the body of a female in the adult condition 140 hours after infection shoving 
the oviduct. 
Fig. 36. Posterior half of the body of a female in the second parasitic stage 85 hours after infection 
showing the whole reproductive system at'this stage. 
