394 APPENDIX. 



much shorter than the second), then three jaws, and three jaw- 

 feet, then five very long legs (the three fore ones of which, in 

 the Peneus, are furnished with nippers, and the third of which is 

 the longest). Finally, on the first five joints of the hinder part 

 of the body there are other five pairs of feet. This shrimp, 

 which is one of the most highly developed and perfect crabs, 

 originates (according to Fritz Miiller's important discovery) out 

 of a naupHus (Fn Plate VIII.), and consequently proves that 

 the higher Crustacea have developed out of the same form 

 as the lower ones, namely, the nauphus. (Compare vol. ii. p. 175). 



Plates XII. and XIII. (Between pages 200 and 201, Vol. II.) 



Blood relationship hetween the Vertebrata and the Invertehrata. 

 (Compare vol. ii. pp. 152 and 201.) It is definitely established 

 by Kowalewski's important discovery, which was confirmed by 

 Kupffer, that the ontogeny of the lowest vertebrate animal — the 

 Lancelet, or Amphioxus — agrees in all essential outlines com- 

 pletely with that of the invertebrate Sea-squirts, or Ascidise, 

 from the class of Sea-sacks, or Tunicata. On our two plates, 

 the ascidia is marked by A, the amphioxus by B. Plate XIII. 

 represents these two very different animal-forms in a fully 

 developed state, as seen from the left side, the end of the mouth 

 above, the opposite end below. Hence, in both figures the dorsal 

 side is to the right, the ventral to the left. Both figures are 

 slightly magnified, and the internal organisation of the animals 

 is distinctly visible through the transparent skin. The full- 

 grown ascidia (Fig. A 6) grows at the bottom of the ocean, 

 from whence it cannot move, and clings to stones and other 

 objects by means of peculiar roots (w) like a plant. The full- 

 grown amphioxus, on the other hand (Fig. B 6), swims about 

 freely like a small fish. The letters on both figures indicate the 

 same parts : (a) orifice of the mouth ; (&) orifice of the body, or 

 poms abdominalis ; (c) dorsal rod, or chorda dorsalis ; (d) intes- 

 tine ; (e) ovary ; (/) oviduct (same as the sperm-duct) ; (g) spinal 

 marrow ; (h) heart ; (/) blind-sac of the intestine ; Qc) gill 



