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1. On the peculiar Appendage of Appendicularia, named 
“ Haus” by Mertens. By Professor Allman. 
In this communication the author called attention to the fact of 
his having discovered, in April last, in the Clyde, near Rothesay, 
numerous specimens of an Appendicularia, invested with the re- 
markable appendage, named ‘ 6 Haus” by Mertens, who originally 
described it in specimens captured in the North Pacific, near Behr- 
ing’s Straits, but which no one since his time had seen, though Ap- 
pendicularia had become a subject of careful and elaborate investi- 
gation in the hands of several of the leading zoologists of the present 
day.* 
The appendage under consideration agreed in its more essential 
details with that originally described by Mertens, except that no 
trace could be detected of the remarkable vascular network which 
Mertens describes as constituting so striking a feature in the speci- 
mens examined by him. There were also some differences in de- 
tails of less importance, — such as in the size of the “ Haus,” which 
was here much smaller than in the Behring’s Straits specimens, 
and in the number and shape of the bodies named “ horns” by 
Mertens, — differences, however, which Professor Allman thinks 
may be referred to a difference of species in the specimens. The 
author also stated, that he had never witnessed the rapid renewal of 
the “ Haus” after complete destruction, a phenomenon described by 
Mertens as constant. 
Notwithstanding, however, these differences, Professor Allman 
had not the least doubt that the structure now described is the same, 
except specifically, with that originally described by Mertens. 
2. Additional Observations on the Morphology of the Repro- 
ductive Organs in the Hydroid Polypes. By Professor 
Allman. 
This communication was intended by the author to be in con- 
tinuation of a former paper on the same subject, read before the 
* Dr S. Wright has since informed the author, that during the past autumn 
he observed Appendicularia in the Firth of Forth, invested with its “ Haus.” 
