The Presidenfs Address. 
51 
in our knowledge of the Polycystina ; for, although long 
familiar to the microscopist as most beautiful and prized 
objects of study, they had not previously received anything 
like a natural and systematic arrangement. But Dr. Wallich^s 
paper claims notice on other grounds, inasmuch as it treats 
not only of this single family, but of the Khizopods generally, 
and recommends for adoption a revised classification of the 
entire group, based on personal examination of the several 
families, and supported by a large number of original and 
highly interesting observations. 
Whilst speaking of Polycystina, I wish to direct attention 
to the drawings of Mrs. P. S. Bury, who has most kindly 
favoured me with copies of her drawings of Polycystins, which 
are evidently, as she tells me, the honest representation of the 
objects as conveyed to her eyes and mind by attentive con- 
templation of the objects seen in a good binocular microscope. 
These drawings illustrate how ladies may assist us in our 
pursuits, and at the same time, I feel sure, give to themselves 
great pleasure in dwelling over and recording faithfully some 
of the variations of forms of growth which are so numerous, 
sometimes whimsical, and often exceedingly beautiful, as are 
shown in Mrs. Bury^s drawings of those curious organisms. 
The subject of the generative productions in invertebrata 
does not seem to have been much taken up by naturalists. 
The paper by Mr. A. Sanders is therefore the more valuable. 
He says, as far as his researches have extended, he has only 
met with two papers treating especially on the development 
of Zoosperms ; they are in De Quatrfefage^s series of papers 
on the Annelida, in the ' Annales des Sciences Naturelles -/ 
there is indeed a paper by Von Siebold in ^ Miiller's Archiv,^ 
1835 and 1836, in which the zoosperms of difierent classes of 
animals are described, but there is nothing about their 
development. In this inquiry there is a great deal of physio- 
logical interest; but perhaps it would be somewhat too 
audacious to hope that it would throw any light on the 
mysterious changes which the physical forces undergo in their 
passage through organic matter, which we call vitality. 
In the Pulmogasteropoda, to which his paper was more 
particularly devoted, the subject is complicated by another 
factor, viz.. Hermaphroditism; and the older naturalists dis- 
puted as to whether the zoosperms and ova were generated in 
the same or in different glands: the balance of evidence 
inclined in favour of the former view, and such is the modern 
received opinion; but it was open to objection, and was ob- 
jected to in a paper by Dr. Lawson, and until the actual 
development of zoosperms could be demonstrated in the 
