88 E. RAY LANKESTER, ON GREGARINIDE. 
Ameebiform bodies, then, described by Lieberkiihn cannot be 
considered as the young stage of the Gregarina. It is possible, 
however, as M. Milne Edwards has observed, that some of 
these bodies, which are hardly distinguishable from the 
true plasmic corpuscles, are developed from the Psendo-na- 
viculz. I have made careful examination of more than a 
hundred worms for the purpose of studying these questions, 
but have succeeded in arriving at no other conclusion than 
that certain forms of these corpuscles may be the products of 
encysted Gregarine. The Gregarina Lumbrici (fig. 25) is one 
of those forms which are unilocular, and are met with most 
frequently among Annelids. It consists of a transparent 
contractile sac (which has not hitherto been demonstrated to 
be formed by more than a single membrane), enclosing the 
characteristic granules and vesicle. The vesicle is not always 
very distinct, and is sometimes altogether absent ; occasion- 
ally it contains no granules, sometimes several, one of which 
is generally nucleated (figs. 25, 26). The average length 
is z45th of an inch. Many varieties are met with in the 
Lumbricus, but there appears to be no reason for considering 
them as distinct species. In figs. 26, 27, a rather uncommon 
form isdrawn. It is much smaller than that drawn in fig. 25, 
measuring from z45th to 345th of an inch in length, and is 
provided with a number of motionless filaments ; there are 
few granules in the interior, but one of them is always nucle- 
ated. Another form (fig. 28), which I have only met with 
twice, contains the vesicle and granules, and is further sur- 
rounded by a number of conical bodies which seem to 
form a sort of envelope enclosing it. -Lieberkiihn, who has 
seen both these forms, calls them “ Gregarines velues,” and 
has observed them in the act of casting off this remark- 
able covering. Frequently in the examination of the testis 
of the Lumbricus, two Gregarine of the larger, well-developed 
form may be seen enclosed in a transparent cyst, varying in 
size from the 75th to ztoth of an inch in diameter 
(fig. 21). Occasionally a single individual appears in this 
condition. In some of these cysts a number of nucleated 
cells may be seen developing from the enclosed Gregarine, 
which gradually become fused together and broken up, until 
the entire mass is converted into these nucleated bodies, which 
are then evident in different stages of development, 
(figs. 22, 23), assuming the form of a double cone, like that 
presented by some species of Diatomaceze, whence their name 
Pseudo-navicule. At length the cyst contains nothing but 
Pseudo-navicule, sometimes enclosing granules, which 
gradually disappear (fig. 24). Finally the cyst bursts. 
