PLATE XXIII. 



Fig. 



1. Pale oily region with germinal vesicle (a) and germinal dot (b), in an ovum removed from the 



body of the female Lineus gesserensis. X 350 diam. 



2. Flask containing two ova from the mucous cord of the same species after deposition. One 



is simply outlined, but the other is shaded— to indicate the natural opacity, x 55 

 diam. 



3. Flask on the second day, showing the yolk divided into four portions. X 55 diam. 



4. Ovum some hours older and somewhat compressed, exhibiting the further subdivision of the 



yolk. X 55 diam. 



5. Flask having its single ovum in the mulberry-stage, x 55 diam. 



6. Flask containing three ova in the same condition. X 55 diam. 



7. Flask having a ciliated embryo (about the 12th or 13th day); it remains in this condition 



some weeks, x 55 diam. 



8. Flask enclosing two young animals, somewhat compressed. a, embryo forced from its 



ciliated cellulo- granular fatty coating, the bulk of which lies at c ; b, embryo still within 

 the ciliated coating. X 55 diam. 



9. A young specimen of L. gesserensis immediately after leaving the flask; b, opening of the 



right cephalic sac. X 90 diam. 



10. Magnified view of a young example of the same species after it has attained a considerable 



degree of advancement. It still possesses only two eyes. 



11. Flask from the mucous cord of Lineus marinus* The contained embryos are nearly disin- 



tegrated from decomposition. X 55 diam. 



12. Ovum of Cephalothrix linearis immediately after deposition. X 350 diam. 



13. Embryo of the same species shortly after extrusion from the egg. X 350 diam. 



14. A young specimen two days older than the preceding, a, mouth ; b, granules of digestive 



cavity. X 210 diam. 



15. An example about three days older than the last (fig. 14). X 210 diam. 



16. A young specimen of Cephalothrizc linearis after shedding the long anterior whip of cilia, 



but having the lateral tufts (c) and eyes, a, mouth ; b, granules of digestive cavity. 

 X 210 diam. 



17. Transverse section of the proboscis of Cerebratulus angulatus, O. F. Muller. g a, the inner 



wedge of longitudinal fibres described in the text ; g b, the outer band of longitudinal 

 fibres. The other letters as usual. X 40 diam. 



18. Stylet-region of Ampliiporus Jiastatus, somewhat contracted. It has the same letters as other 



figures of the Enopla. X 55 diam. 



19. Stylet-region of Ampliiporus bioculatus. X 55 diam. 



