276 



ZOOLOGY 



into a sac ; this in turn opens by a duct lined with chitin at 

 the base of the first thoracic appendages. The walls of this 

 sac appear to secrete the cement by means of which the ova 



Fig. 163. — A view of Lepas 

 anatifera, out open longi- 

 tudinally to show the dis- 

 position of the organs. 

 From Leuckart and 

 Nitsche, partly after Claus. 



1. Stalk. 



2. Carina. 



3. Tergnm. 



4. Scutum. 



5. Antennae. 



6. Mandible with " palp " in 



front. 



7. 1st maxilla. 



8. 2nd maxilla. 



9. The six pairs of biramous 



thoracic limbs. 



10. Labrum. 



11. Mouth. 



12. Oesophagus. 



13. Liver. 



14. Intestine. 



15. Anus. 



16. Ovary. 



17. Oviduct. 



18. Testes. 



19. Vas deferens. 



20. Penis. 



21. Cement gland and duct. 



22. Adductor soutorum 



muscle, which closes 

 the shell. 



23. Mantle cavity. 



are bound together. It will be noticed that the opening of 

 the oviduct is situated much farther forward than in other 

 Crustacea. It lies in the segment which succeeds that 

 upon which the excretory organs open, and it has been sug- 

 gested that the sac and its duct may possibly represent an 

 original segmental organ. 



The ova when laid are cemented together, and form in the 

 Lepadidae flattened masses which are attached to a fold of the 

 mantle, and form very obvious structures easUy seen when the 

 shell is opened. 



In spite of the fact that, with few exceptions, the Cirrhi- 



