ON THE ANATOMY AND DEVELOPMENT OF PYROSOMA = 323 
especially as in fig. 9 it lies in the saine place as that in which I have 
always found it, viz. in the large mid-atrium and altogether behind 
the intestine. M. Vogt concludes by putting forward the hypothesis 
that the ova pass down the canal of the ovisac into the neighbourhood 
of the intestine, where an incubatory cavity, in which their final 
development takes place, is formed for them in the thickness of the 
inner tunic. 
“This incubation, perhaps, takes place only during certain periods 
of the year, or of the life of the zooid, whence the incubatory cavity is 
found only in some individuals and not in all. The formation of ova 
in the projecting ovary would continue for a certain time. The ova 
would pass, as they became fecundated, into this incubatory cavity, 
would develope there, and would ultimately be set free to lead an 
independent existence. Perhaps, indeed, the incubatory sac may 
be thrown off bodily, and thus give rise to the base of the new 
cylinder.” (4 ¢. p. 90.) 
These observations and suggestions obviously leave much room 
for further inquiry, and my satisfaction will be easily understood 
when that opportunity of renewing my investigations which I desired, 
but little expected, was unexpectedly afforded me. In October of 
the year 1859, Rear-Admiral FitzRoy, F.R.S., the indefatigable 
Superintendent of the Marine Department of the Board of Trade, 
kindly forwarded to me a very beautiful specimen of Pyrosoma 
giganteum, taken by Captain Callow! in the North Atlantic, about 
400 miles S. of the Cape De Verd Islands, in the month of August of 
that year, and admirably preserved by immersion in strong spirits. 
I was aware, from former experience, that the textures of Ascidians, 
in general, are admirably conserved in spirit-specimens which are 
even many years old; and I therefore commenced my inquiries with 
a sanguine expectation of being able to make out something about 
the origin of the compound embryos, which a cursory inspection of the 
specimen proved to exist in abundance. I must confess, however, 
that I had no anticipation that researches conducted upon a preserved 
specimen of any animal could be followed out so far as I have been 
led, step by step, to carry these. And had I not had the opportunity 
of showing many of my preparations to observers of experience and 
authority, who can bear witness, at any rate, to the perfect distinct- 
ness of the most important of the appearances described, I should 
hardly have hoped to secure a patient reception for delicate embryo- 
1 Finding a specimen could be procured in no other way, this gallant and skilful seaman 
swam for that he obtained. He informs me that it emitted « strong bluish-white light, 
sufficient to read small print by. 
ae 
