Fisurforldnrino-. 



For samtlige fig. gjælder folgcnde Ijetegnelsei-: 



Eg = Egestionsaabniug, 

 Ekt = Ektoderm, 



El = Eleoblast, 

 End = Endostvl, 

 Ent = Entoderm, 



Fl = Flimmersom, 

 G = Ganglion. 



JI = Hypofysis., 



Kd = Gjællesæk, 



Ks = Gjællespalte, 

 Ing = Ingestionsaabning, 

 Mes = Mesoderm, 

 Nr = Nerverør, 

 Nv - Nerve, 

 Ov = Æg, 

 Phc = Peribranchialcaviteter. 

 T = Tarmanlæs. 



Fis 



1—6. 



Tab. VII. 



Snitserie gjennem knop af Stadium I (Ret- 

 ningen betegnes ved linierne paa tig. 7). 

 Sclienia for en knop af Stad. I. 



-.-,.-. II. 

 Snitserie gjennera knoji af samme stadium. 



Scbema for knop af Stad. III. 

 Snit gjennem knojj af samme stad. 



Tab. VIII. 

 Schema for knop af Stad. IV. 

 Snitserie gjennem knop af samme stad. 



Snit ,, ,, - ,, „ 



Schema for knop af stadium V, set bagfra 



og fra siden. 



Fortykket nerverør. 



Hjerner af næsten fuldt udviklede knopper. 



Schema for knop, noget reldre end stad. V. 



Snitserie gjennem en saadan knop. 



Expliuiatioii of the Figiires. 



The following lettering is used in all the figures: 



Eg = atrial aperture. 

 Ekt = ectoderm. 

 El = elæoblast, 

 End = endostyle. 

 Eld = endoderm. 

 Fl = peripharyngeal bant 

 (r = ganglion. 

 H = hypophysis, 

 Kd - branchial sac. 



Ks = brancliial stigmata. 

 Ing = oral aperture, 

 Mes = mesoderm. 

 Nr = nerve tube, 

 Nv = nerve, 

 Ov = ovura, 



Phc = periliranchial cavities. 

 T - rudimentary intestine. 



Figs. 1 — 6. 



Fig. 7. 

 Fig. 8. 

 Figs. 9—15. 



Fig. 16. 

 Figs 17, 18. 



Fig. 19. 

 h Figs. 20—25. 



Fig. 26. 

 Figs. 27. 28. 



Fig. 29. 

 Figs. 30 -S2. 

 Fig. 33. 



Pigs. 34—37. 



Pl. VII. 



Series of sections through n liud of Stage I 

 (Sectional plane indicated by lines in iig. 7). 

 Diagram of a liud in Stage I. 

 ,. -..../ II. 

 Series of sections tlirough a bud in the 

 same stage. 



Diagram of a bud in Stage III. 

 Section through a bud in Stage III. 



Pl. VIII. 

 Diagram of a bud in Stage IV. 

 Series of sections tlirougli a bud in the 

 same stage. 



Sectiou through a liud in the same stage. 

 Diagram of a bud iu Stage V, seen from 

 behind and from the side. 

 Thickened nerve tube. 

 Ganglia of almost fuUy developed buds. 

 Diagram of a bud in a rather more advan- 

 ced stage than Stage V. 

 Series of sections tlirough such a bud. 



