184 LEUCKART, ON PENTASTOMUM TANIOIDES. 
size and formation, the males, only two of which were found, 
showed an entire agreement with the male Pentastomata 
of the second dog; they had evidently gone through their 
whole development two months before. But this was not 
the case with the three females found with them, which 
since that time had grown to more than double their 
former length (up to 65 mm.), and had also arrived in the 
mean time at complete sexual maturity. Not only were 
their ovaries full of ova in various stages of development, 
but the vagina, which measured nearly one millimetre, was 
filled with them; and to such an extent was this the case, 
that, according to a very moderate estimate, their number 
could be calculated at fully half a million. As might be 
expected, the ova in the vagina were all mature—nay, more, 
they were even all fertilised, as might be concluded not only 
from the circumstance that, before their entrance into the 
vagina, they must pass the openings of the two seminal 
pouches above mentioned, but especially from the considera- 
tion that they already exhibited unmistakeable signs of a 
commencing development of the embryo at a small distance 
from the upper end of the vagina. ‘The lower fifth of the 
vagina even contained ova with fully mature embryos. 
The embryos of these Pentastomata were examined and 
described several years ago, in Utrecht, by the late helmin- 
thologist Schubart.* In all essential points they exhibit the 
same structure which Van Beneden had previously found 
in the embryos of Pentastomum proboscideum parasitic in 
several species of snakes. They are so strikingly different 
from the fully formed Pentastomata, that, in examining 
them, we are reminded of certain Acarina and allied forms, 
far rather than of the vermiform parasites now under consi- 
deration. 
The body of the embryo consists of two distinctly sepa- 
rate parts—a short and broad, egg shaped anterior part 
(0:07 mm. long, 0°05 mm. broad, and about the same in 
height), and a rather long, slender tail (measuring 0°056 mm. 
long and 0:010 broad), which, during its stay in the ovum, is 
invariably folded on the ventral surface. On the contrary, 
in the embryo of Pentastomum proboscideum—and I observe 
the same in a second species discovered by Professor Harley 
in London, from the lung of an African snake, the P. multi- 
cinctum, Harl., the embryos of which also in other respects 
agree almost entirely with those of P. proboscideum—the tail 
is much shorter, and separated from the rest of the body in a 
* ¢Zeits. fiir wissenschaft. Zool.,’ 1852, Band iv, s. 117. 
