WALKER-ARNOTT, IN REPLY TO DR. DONKIN. 89 
Mertens’ species, differs considerably from that of the fans in 
the present one. Still there can be no doubt that the 
“haus” of Mertens is the exact equivalent of the body now 
described, and the differences seem to be merely traceable to 
a difference of species. 
If I might offer an opinion as to the real import of the 
“haus,” I would suggest the probability of its being a de- 
finitely shaped secretion, destined to act as a nidamental cover- 
ing for the ova. I do not wish, however, that this sug- 
gestion should be taken for more than it is worth, for it is 
chiefly based on the circumstance that it is difficult to offer 
any other explanation, and on the fact that in one instance 
I found numerous minute and evidently young, though nearly 
fully developed, Appendicularie immersed in the gelatinous 
mass of the haus. Beyond this I shall not venture even a 
guess at its physiological or morphological significance.* 

Dr. WaLKER-ARNoTT, in Repiy to Dr. DonkIN. 
In the last number of the Journal appeared an article 
purporting to be a reply to me by Dr. Donkin, but which 
contains, in fact, a repetition of some observations respect- 
ing Ampiphrora Ralfsii, published by him in the ‘ Transac- 
tions of the Microscopical Society’ in January, 1858, p. 33. 
I allude more particularly to what he erroneously states 
with regard to the name of Amphiprora Ralfsti being mine 
generically as well as specifically. 
It might be sufficient to indicate that I communicated 
the specific name to Mr. Ralfs; that Dr. Donkin’s infor- 
mation was not obtained from me, but must have been 
derived directly or indirectly from Mr. Ralfs; and that every 
one acquainted with Mr. Ralfs’ writings knows that his 
* The above account was drawn up immediately after the observations 
which it records were made. I however delayed its publication under the 
expectation that I might have an opportunity of obtaining fresh examples 
which would enable me to supply some of the many deficiencies which exist 
in it. No such opportunity has since occurred, and I have, therefore, not- 
withstanding its imperfect form, thought it better to publish it as it is, with 
the hope that it may be of some use in enabling other naturalists to render 
more complete our knowledge of a structure which at best is highly enig- 
matical. Dr. Strethill Wright, of Edinburgh, informs me that during the 
autumn he obtained in the Frith of Forth specimens of an Appendicu- 
aria invested with its “haus.” 
