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 
Fic. 163.—A view of Lepas 
anatifera, cut open longi- 
tudinally to show the dis- 
position of the organs. 
From Leuckart and 
Nitsche, partly after Claus. 
1. Stalk. 
2. Carina. 
3. Tergum. 
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 scutorum 
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 les 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 easily seen when the 
shell is opened. 
In spite of the fact that, with few exceptions, the Cirrhi- 
