; ee. a 
- pike. ” 
68 : THE MICROSCOPE, 
the new order of Auronectze Haeckel, an enlarged axis by which the 
polypites and other organs are brought into contact with the water. 
Respiration probably takes place over the whole surface of the body 
in all the Medusz, aerial by means of an elaborate tracheal system 
in Velella or the enlarged float in Physalia and Rhizophysa, or 
aquatic through the covering scales, nectocalyces and other organs 
in Agalma and others. If the function of respiration belongs to 
the scales, it may be well to inquire whether the color cells have any 
relation to it. Their absence in most Physophores would seem to 
have a negative bearing in an answer to this question. 
The covering-scales have been homologized with portions or 
fragments of swimming-bells. A. Agassiz compares them in Nano- 
mia to the spheromere of a gelatinous bell, and finds in Hybocodon 
a medusa presenting an asymmetrical reduction of its bell, which is 
significant in the determination of their homology. The genus 
Athoria of Haeckel would seem to show that the covering scales are i 
homologous to the apex of a medusa bell, for in this genus we haye 
a bell cavity with radial tubes at the distal tip of a well developed 
bract. Accepting this interpretation, the central canal would seem 
to correspond perfectly, not with the radial canal as A. Agassiz’s 
theory would necessitate, but with the central apical canal of a lar- 
val medusa before its rupture from a hydroid, or the same central 
canal of a nectocalyx. The cluster of nematocysts at the free end 
of the scale would thus represent the remnants of the tentacles, to 
which homology the large size of the lasso-cells in the half devel- 
oped scale adds some weight, as does likewise the character of the 
covering-scale of EKudoxia and Praya. 
On the other hand it is worth our consideration, in the study of 
the homology of the covering-scale, to remember that in the genus Pte- 
rophysa we have lateral wings on the polypites and we may suppose 
if these lateral wings became very much enlarged we would have an 
organ very similar to the covering-scale of Agalma. On the other 
hand, if the covering-scale was reduced, it might readily be converted 
into a simple tubular body such as we find in certain forms of the 
tasters. We have then the probability that tasters and hydrophyllia 
are homologous, although their form is so different, and we see that 
in some genera they have the same power of discharging a colored 
fluid from certain glands. The structure of the base of 
the taster* of Nanomia is different from that of other Physo- 
*The division of the taster of Physophores into three kinds—those with tentacles and 
closed distal ends,those with open extremities without tentacles and those which bear 
at their bases the sexual bells—seems necessary and requisite to designate the different 
functions which they appear to have. The so-called tasters of Nanomia would seem to 
belong to the second of these three divisions, or to the cytons of Haeckel’s descriptions of 
the anatomy of the Physophores. 
