426 REPORT—1863. 
But, to convince ourselves of this difference, it is not necessary to include 
in our comparison the fixed sac-like gonophores at all; for if we confine our- 
selves to those cases in which the comparison lies between free medusse on 
the one hand and the trophosomes from which they spring on the other, we 
shall still find that the doctrine which would always refer similar medusee to 
similar trophosomes, and similar trophosomes to similar medusz, though in a 
large proportion of cases it holds good, cannot be absolutely maintained. 
On this point we have an important observation made by Hincks, who 
found the medusxe produced by the Stawridia prodwta, Wright, indistin- 
guishable from those of Coryne ewimia, Allm., and yet the two trophosomes 
have justly been regarded as presenting generic differences. 
Again, we are not without cases of the converse of this phenomenon, that 
is, cases of trophosomes closely resembling one another, and yet producing 
widely different medusze. Compare in this respect the Coryne eximia, Allm., 
and the Coryne impleva, Alder. No one would venture, from a com- 
parison of the trophosomes alone, to place these hydroids in different genera ; 
and yet their medusz are separated from one another by characters which, 
if we were treating organisms originally independent, would be regarded as 
at least generic ; for while the medusa of Coryne eximia would, in accord- 
ance with the received classification, be an Oceania*, that of C. implexa 
would be a Zanclea, Gegenb. 
Far more rare than the cases in which known meduse have not yet been 
referred to known trophosomes are those in which the gonosomes of known 
trophosomes have not yet been discovered; and even these will rapidly dis- 
appear under the laborious scrutiny to which the whole of this department of 
zoology is now being subjected. Until this happens, however, our charac- 
terization of species cannot be otherwise than incomplete; for no such 
group can be valid which is founded only on one part of every individual 
composing it, the other part remaining unknown. 
An Account of Meteorological and Physical Observations in Five 
Balloon Ascents in the year 1863 (in continuation of eight made in 
the preceding year), under the auspices of the Committee of the 
British Association for the Advancement of Science, by Jamus 
GuatsHEeR, /.RS., at the request of the Committee, consisting of 
Colonel Sykes, the Astronomer Royal, Lord Wrottesley, Sir D. 
Brewster, Sir J. Herschel, Dr. Lloyd, Admiral FitzRoy, Dr. Lee, 
Dr. Robinson, Mr. Gassiot, Mr. Glaisher, Prof. Tyndall, Dr. Fair- 
bairn, and Dr. W. A. Miller. 
Tur principal efforts of the Committee in this series were the extension of the 
experiments began last year to the spring months, and particularly during the 
prevalence of easterly winds. 
§ 1. Ossecrs or run Experiments: Instruments AND APPARATUS: 
Were the same as those detailed in the preceding Report; in addition, how- 
ever, Sir John Herschel’s actinometer was used when possible for the purpose 
of determining the actinic effects of the sun at different elevations; and on 
two or three occasions the solar spectrum was examined by means of a spec-- 
troscope, lent for the purpose by the Astronomer Royal, being the same in- 
* In the sense in which this genus has been limited by Forbes. 
. 
