Lagenorhynchus acutus. Gray. 



Fig. 1. An 8 millim. long foetus ol' Lagenorhynchus acutus, Gray. Magnified. The embryo is lying with the left 



side up in situ in the amniotic bag, which is opened. Am. am. = flaps of amnion; all = allantois; k = umbilicus 



and umbilical cord (?); c = cauda; Fp. = foremost part of the body; h = vesicle-like expansions. Drawn 



by Dr. F. Nansen. 

 ,, 2. The ventral surface of the same embryo, deformed, c = cauda, which is very long and bent; n = umbilicus. 



Magnified 8 times. Drawn by Dr. F. Nansen. 

 ,, 3. Right side of the same foetus. F = foremost part of the body, which is injured and deformed: v = ventral 



surface; d = curve of the dorsal surface; u = umbilical cord; c = cauda, above which is a blind hollow. 



Magnified 8 times. Drawn by Dr. F. Nansen. 

 „ 4. Back of the same foetus. F = foremost, injured part of the body; H = hindmost, uninjured part. Magnified 



8 times. Drawn by Dr. F. Nansen. 

 „ .5. Sagittal section through the same foetus. The section is considerably to the outside of the median plane. The 



details of the anterior part of the foetus are not shown in the drawing. Sey = proto-vertebrie ; c = cauda; 



a = anal depression; u = umbilicus; d. a = allantoic passage; hep = liver; cor = heart. Drawn by Prof. 



G. Guldberg. with Zeiss obj. A* oc. no. 2. Abbe's camera lucida. 

 ,, 6. Median section through the same fætus. Seg 1, seg 2, seg 3 = proto-vertebræ in the foremost, middle and hind 



parts of the body; ch, = chorda dorsalis: med = medullary tube; ch = brain vesicle enlargement; F t ^ 



fore-gut; cor = heart; hep = liver; t = gut (?); u = umbilicus; a = anal depression. Drawn by 0. Bergh, 



medical student. 

 „ 7. Hind end of the same fætus, showing the invagination of the ectoderm for the formation of the anus, in a section 



to the side of the median line. c = caudal end; med = medullary tube; a = anal depression. Zeiss obj. aa 



oc. 2, Abbes camera lucida. Drawn by Prof. G. Guldberg. 

 „ 8. Section of the integument on the dorsal surface of the same fcetus, above the medullary tube. e^i = epidermis; 



de = corium; med = medullary tube. Drawn by Prof. G. Guldberg. 



