E. RAY LANKESTER, ON GREGARINIDA. 85 
of a single cell; their membrane corresponds to a cell-mem- 
brane; their contents to cell-contents; their vesicle to a 
nucleus; the granule or granules within it to a simple or 
broken up nucleolus. 3rdly. The Gregarine, which are con- 
stricted at the middle, also correspond most probably with a 
single cell of a peculiar kind. 4thly. There is no reason what- 
ever for supposing that the Gregarine are not perfect animals. 
These four assertions have been questioned by various authors 
since that time. C. Bruch, in ‘Sieb. and KOll.,’ vol. ii, p. 
110, opposed the last-mentioned assertion of Kolliker, and 
was inclined to regard the Gregarine as Filariz in a quiescent 
state. Dr. F. Leydig, in Miiller’s ‘ Archiv’ for 1851, brought 
forward what was apparently very strong evidence in favour 
of Bruch’s theory, having seen the successive development 
of a simple quiescent Gregarina into an active vermiform 
creature, which he considered as a nematode.  Kolliker, 
however, replied to this that he regarded the form de- 
scribed by Leydig as an Infusorium allied to Opalina or 
Proteus. It appears from the researches of M. Claparéde 
and others, within the last few years, that some of the uni- 
locular forms of Gregarinz do present very curious, elongated, 
and active forms, which from their movements and general 
appearance might be mistaken for nematodes. Dr. Joseph 
Leidy has in the ‘Transactions of the Philadelphia Society,’* 
denied the fact that the Gregarine are unicellular animals, 
upon the following grounds. In the examinations of some 
new species of Gregarinze which he has described, and aiso 
in the Gregarina Blattarum of Siebold, he discovered that 
the membrane enclosing the granular mass of the posterior 
sac was double. He observes, “ Within the parietal tunic of 
the posterior sac is a second membrane, which is transparent, 
colourless, and marked by a most beautiful set of exceedingly 
regular parallel HOE RE ae lines, which in G. Juli: mar- 
ginatt measure the ,,',,rd of an inch apart; in G. Blatte 
orientalis the 7, ehh of an inch; and in G. Passali 
cornutt the >=}, «th of an inch. This tunic has entirely 
escaped the notice of all previous observers, and I can account 
for the circumstance in no other way than by supposing it 
has arisen from the inferiority of the microscope made by 
European continental artists. The lines or markings are 
easily observed without any other then the erdinnry, arrange- 
ments for light by 4 of an inch, but better the =, of an inch, 
focal power of the instr ument of Messrs. Powell ae Lealand. 
Of course, if the existence of this second tunic be confirmed, 
and I have seen it too frequently and plainly to think I have 
* «Trans. of Phil. Society,’ 1853. 
