464 BAUR. [Vot. III. 
I have nothing to change in these general results, but can 
add some important facts relating to numbers 4 and 5. 
The connection between higher vertebrates and fishes is found 
to be the condition represented by LEPIDOSTEUS. 
Up to this time the difference in the tail of fishes and the 
higher vertebrates appeared to be a fundamental one. In fishes 
the “hamal arches” which enclose the subcaudal blood-vessels 
are either formed by true ribs, or by the prolonged parapophyses 
to which the ribs are united. In all higher vertebrates the ribs 
are entirely separated from the ‘“hamal arches”; they are 
placed above these on the side of the vertebrae. The following 
diagrams represent the two conditions :— 
al m, neuroid. 
( )p wa C™~ _ A; parapophysis. 
P pl, pleuroid 
, pleuroid. 
pl a a, chevron, 
I 2. 
1. Caudal vertebra of Fishes. 
2. Caudal vertebra of higher Vertebrates. 
It is evident that the “hamal arch” of fishes, which is either 
composed of pleuroids, or of pleuroids and parapophyses, can- 
not be the homologue of the “ hzmal arch” of the higher ver- 
tebrates. The question is, what elements of the fish’s skeleton 
are used in the formation of the “hzmal arch” of the higher 
vertebrates; in other words, what are the homologues of the 
chevron bones ? 
The original condition is, that the subcaudal blood-vessels are 
surrounded by the pleuroids, in the same way as the neural 
cord is surrounded by the neuroids. In the higher vertebrates 
the pleuroids have moved dorsad, and have become entirely 
independent from the blood-vessels. In fishes the pleuroids are 
connected with the parapophyses (“ Basalstuempfe’”’ Goette) of 
the vertebra. The condition found in the higher vertebrates 
could be developed by two different ways: either the parapo- 
