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 nauplius (#7 Plate VIII.), and consequently proves that 
the higher Crustacea have developed out of the same form 
as the lower ones, namely, the nauplius. (Compare vol. ii. p. 175). 
Puates XII. anp XIII. (Between pages 200 and 201, Vol. II.) 
Blood relationship between the Vertebrata and the Invertebrata. 
(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 Ascidie, 
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; (bd) orifice of the body, or 
porus abdominalis; (c) dorsal rod, or chorda dorsalis; (d) intes- 
tine; (e) ovary; (f) oviduct (same as the sperm-duct) ; (g) spinal 
marrow; (hk) heart; (¢) blind-sac of the intestine; (&) gill 
