Piate 6. 



Endoparasitic deyelopment of Peltogaster. Complemental Males of Sacculina. 



The parts of sections tinted red belong to the host. 



Ant Antenna of Cypris. Ap thoracic appendage. b.c brood pouch or mantle cavity. eh chitin. ch.ext 

 external chitin of host. ci cloaca or mantle opening. et centrai tumour. Ec Ectoderm of Cypris. Ect Ecto- 

 derm of host. Em embryonic cells of Cypris. epl internai epithelium of brood pouch. ep2 external epithelium 

 of brood pouch. ep3 external epithelium of mantle. liv liver of host. mes mesentery. n nucleus from which 

 visceral mass is formed. muse muscle. ov ovary. r roots. sj) spider cells. t testis. vis.mass visceral mass. 



Fig. 1. Outline drawing of stolon-like tumour of Peltogaster internus, with roots beginning to grow out. 



X 23. 

 Fig. 2. Section through a young Peltogaster internus of about same age as Fig. 1. X 140. 

 Fig. 3. High power drawing of anterior region of tumour marked n in Fig. 1. X 650. 

 Fig. 3a. High power drawing of a root of Peltogaster internus figured in Fig. 1. 

 Fig. 4. Longitudinal section through centrai tumour and body of a Peltogaster internus, in the act of being 



protruded from the body of its host. X 140. 

 Fig. 5. High power drawing of Fig. 4, to show differentiation of organs. X 325. 

 Fig. 6. Transverse section through a young Peltogaster externus. X 40. 

 Fig. 7. Figure from side of Eupagurus prideauxii carrying on its abdomen 22 specimens of Peltogaster 



socialis. X 2. 

 Fig. 8. Lateral view of a single specimen of Peltogaster socialis. X 5. 

 Fig. 9. Section through the centrai tumours of two Peltogaster socialis internus lying within the abdomen 



of the host. X 70. 

 Fig. 10. Section through centrai tumour of a Sacculina neglecta interna, in which are seen two visceral 



masses with their mantle cavities. X 325. 

 Fig. 11. Fourteen Cypris larvae fixed round the cloaca or mantle opening of a young Sacculina externa. X 70. 

 Fig. 12. Section through the mantle opening [ci) of a young Sacculina externa to which are attached Cypris 



larvae. Two of these aTe shown in the figure; one of them contains embryonic cells (Em) which 



pass through the antenna; the other is already empty. X 325. 

 Fig. 13. Longitudinal horizontal section through a Cypris larva found on a young Sacculina externa but 



not yet attained to the mantle opening. X 650. 

 Fig. 14. Transverse section through Fig. 13. X 325. 

 Fig. 15. Longitudinal sagittal section through a Cypris larva fixed near mantle opening of a young 



Sacculina externa; the Embryonic cells pass through the antenna. X 1300. 



