asta pita 
E. Billings on the structure of Crinoidea, etc. 75 
organs, and also, that they are the homologues of the tubular 
apparatus which underlies the ambulacra of the Blastoidea. 
J, Miiller suggested a comparison between these peculiar or- 
gans and the respiratory ages of the Asteride. (Uber den 
bau der Echinodermen, p. 63, 1854.) Prof. Huxley has placed 
them in the same relation. (Medical Times, Dec. 1856.) ne 
wald calls “ eles pores. (Lethaea Rossica, vol. 1 
614, 1860.) Prof. Dana says “ pen are probably connected on 
an aquiferous system and respiration.” (Man. Geol., p. 162, 
1863.) Mr. Rofe, after showing that their structure is the 
same as that of the striated surfaces between the rays of Co- 
daster, says, “‘From the construction of these striations on the 
face of Codaster, and on the ‘ pectinated rhombs’ of the cys- 
tidea, may we without assumption suggest the possibility of 
their ‘being respiratory sacs, lined with cilia, and constructed 
+ ey I am now convinced that the view of the above 
; named dietinirabatesd cathciha is the correct one. These are 
; respiratory organs. In all the species in which they ee 
. they seem to be constructed on the same general plan, i. 
o : 
figs. 4, 5,) between two of the plates. In several of the gen- 
era the two halves of the — are reniform, ovate or 
lunate, and either internal or externa 
5. 6. 
Ae 
fi 
agi’ a 
Ung INS 
* a ‘ q 
a... = Ay 
Fig. 4. on Sap - _Caryocrinus ornatus. surface view, the dots around the 
mar. iracles, the small dotted | lines represent the course of the = 
cana oe ¢,¢, Suture between the two plates; °, transverse 
5. Hydrospire of Pap tites. a, surface view: c, c. : 2b transverse 
section. 6. The same with the points ¢, c, drawn to Sate? 1. Internal gill 
of a spider. 
