350 CONTRIBUTIONS TO THE NATURAL HISTORY 



There is a very marked difference between this species and Bolina elegans of Mertens, 

 in the form of its lateral auricles and in its color, which is not rosy, as in the species from 

 the Pacific, but of a rnilky bluish-white, as in Bolina septentrionalis, with which it agrees 

 in the form of its auricles, differing from it, however, in the less limited development of its 

 longitudinal diameter, in the greater approximation of the two auricles of each side, and 

 in the greater width of the mantle lobes, for which reason I have called this species 

 Boliua alata. 



It is a most delicate, transparent, and diflluent animal ; so soft, that it readily decom- 

 poses under the least unfavorable circumstances. The admixture of a small proportion 

 of fresh water in the bowls in which I used to preserve them caused not only their im- 

 mediate death, but their almost instantaneous decomposition. All my efforts at preserv- 

 ing specimens in Goadby's liquor have entirely failed, and when, under identical cir- 

 cumstances, 1 succeeded in keeping for a long time specimens of Pleurobrachia rhodo- 

 dactyla, I failed in preserving specimens of Bolina alata longer than twenty-four hours. 

 Again, this species being by no means so common as the Pleurobrachia, with which it 

 is found promiscuously, I had to contend with great difficulties in my investigations of its 

 structure. I nevertheless succeeded several times in injecting it with indigo, and though 

 the injection soon caused the death of the animal and its decomposition, I have been 

 able to trace the circulation for a sufficient time to follow the full course of the fluids 

 within the body throughout all its parts ; and being already acquainted minutely with 

 the arrangement of the chymiferous tubes in Pleurobrachia, I was fully prepared to in- 

 stitute between the two genera a minute comparison, to ascertain their differences, and 

 to recognize the homology of their structure. I was even able to trace the connection 

 of all the parts of the chymiferous system more fully in Bolina than in Pleurobrachia, 

 and to ascertain connections between its central and peripheric tubes which I failed 

 to perceive in Pleurobrachia, in which these connections may, however, be wanting 

 to some extent, as has already been mentioned above, when describing Pleurobrachia 

 rhododactyla. 



In order fully to understand the structure of Bolina alata, and the relations of its 

 various parts, it is necessary first to have a precise idea of its external form, which it is 

 by no means easy to acquire, even after repeated investigations. Like Pleurobrachia, 

 the body of Bolina is more or less ovate, but in an inverse direction ; for its greater 

 diameter follows the plane of the corresponding organs in such a connection as to show 



many instances which show that species on the opposite shores of this continent are adapted to the difference 

 which exists in the climatic condition, and tlie different course of the isothermal lines on the eastern and 

 western sides of the Old and New Worlds. 



