BRANCHIAL SENSE ORGANS IN ICHTHYOPSIDA. 145 
tive one, and is only meant to give a general view of the results 
of the researches recorded here. In passing I may remark 
that Dohrn’s recent criticism of Ahlborn’s! paper on this poiny 
seems to me to meet the objectionable points so successfully 
that further criticism is unnecessary. 
In connection with this table the reader would do well to 
consult the three diagrammatic figures (figs. 43, 46,51). The 
same results are there shown. Fig. 43 is a diagrammatic hori- 
zontal section through the various sense organs and ganglia, 
and with fig. 45, which is a side view of the same structures, 
shows the primitive condition. Fig. 45 shows the primitive 
position of these sense organs over the gill-clefts. In it for 
simplicity, the post-branchial nerves are left out. But in fig. 46 
these and the pre-branchial nerves are shown. The closed gill- 
clefts are also given with the absorbed branches in dotted lines. 
Finally, fig. 51 is meant to show the adult condition of the 
supra-branchial nerves, which are very diagrammatically given 
in fig. 46. 
Tue Rewations oF THE BRANCHIAL SENSE ORGANS TO THE 
‘“‘ SEITENORGANE”’ OF CaAPITELLID. 
Eisig? first suggested that these two sets of organs were 
homologous. Since then no one has added anything to the 
grounds for this homology furnished by Hisig. Until now it 
may truly be said that we knew nothing of the morphology of 
these branchial sense organs of Vertebrates. Now we do know 
a little, and this appears to me to place the homology of the 
“ Seitenorgane” of Capitellids with the branchial sense 
organs in avery doubtful light. We have seen that primi- 
tively these branchial sense organs are not found in all 
segments of the body but are limited to the head, that 
they have special ganglia, and are special sense organs of the 
gill-clefts. 
‘ Ahlborn, “ Ueber die Segmentation des Wirbelthier Korpers,” ‘ Zeit. fiir 
wiss. Zool.,’ Bd. xl, p. 309. 
* Hisig, “ Die Seitenorgane u. beckerférmigen Organen der Capitelliden,” 
Mittheil. a, d. Zool. Station zu Neapel,’ Bd. i. 
VOL, XXVI, —NEW SER, K 
