302 REFERENCE TO PLATES. 



29. Posterior extremity of the ejaculatory (e), in continuation with 



the seminal (a) band. b. Membrane of the spermatophore. 



d. Commencement of the spiral membrane. 



30. A middle portion of the ejaculatory baud. a. The envelope, in 



two layers, b. 1 he spiral membrane. 



31. Anterior extremity of the spermatophore. 



32. Extremity of the cup-portion of the hectocotylized arm, with 



the commencement of the lash and opening of the sack. 

 . Lash. b. Muscular band of the lash, continuing in the 

 arm. c. Ganglion, d. Suckers, e, f. External and internal 

 layers of the sack. 



33. The vesicle opened to show the abnormal arm enrolled within 



it. Enlarged twice. 



34. Anterior extremity of the lash. 



35. A portion of the middle part of the lash, considerably enlarged. 



a. Central duct. b. Walls of the muscular tube. e. Skin 

 which envelopes the lash. d. Lateral cutaneous muscles. 



e. Cutaneous ducts. 



Plate 19. 



1. Argonauta Argo eggs. Fer. and Orb., Ceph. Arg., t. 1 ter., f. 2. 44 



2. Group of egg cases of Loligo punctata, Les. Amn. Marine Con- 



chology, t. 3, f. 11 ; . . 45 



3. Egg cases of Octopus punctatus, Gabb. From specimens >. . . 45 



4. 5. Egg cases of Sepia officinalis. Fer. and Orb., Seiches, t. 3, 



f. 3, 3 a . 45 



Plate 20. 



1, 2. Mass of eggs and embryo of unknown cephalopod. Zeit. 



Wiss. Zool., xxiv, t. 39, 40 46 



3, 4, 5. Ribbon-like nidus rolled into a cylinder, and embryo of un- 

 known cephalopod. Ann. Sci. Nat., xx, t. 14 46 



6, 7. Nidus and embryo of Octopus membranaceus. Fer. and d'Orb. , 



Octopus, t. 28 .' . . 46 



8. Embryo of unknown cephalopod. Jour. Linn. Soc., xi, t. 1..... 46 



Plate 21. 



Development of cephalopoda (Sepia officinalis). Keferstein, 1. c., 



t. 123 46 



Explanation of reference letters and figures : 

 D. Outer yolk sack. o. Mouth. m b. Buccal mass. 

 v. Stomach, b r. Branchiae. b i. Ink-bag. c 7i. Shell. 

 J. Siphon. m c. Musculus collaris. c h. Button cartilage. 

 n c h. Neck plate. G' C". Under and upper head flaps. 

 o c. Eyes. 1, 2, 3, 4, 5. Arms. 



1. Three stages of the u foldings " of Kolliger, prior to oviposition. 



2. An egg, somewhat magnified. 



3-5. Eggs showing stages of segmentation. 



6, 7. Eggs with the capsules cut open, showing the embryos. 



8-13. Progressive stages of segmentation. 



14-15. Front and side view of Kolliger' s fourth stage of develop- 

 ment. 



16. Embryo in sixth stage. 

 17-19. Embryo in seventh stage. 



