384 C. H. MARTIN. 
are formed, radiating from a central mass, and each termi- 
nating in aciliated bud. ‘The nucleus in the internal parasite 
is a rounded homogeneous mass, which can be readily distin- 
cuished in stained preparations from the branched coarsely 
granular nucleus of its host. Under very high powers in 
material fixed with Flemming’s solution it could be seen that 
the nucleus of the internal parasite is also very finely 
granular. 
The ciliated spores (PI. VIII, fig. 7) are more or less oval 
bodies, about ‘(04 mm. long by °018 mm. broad, with a patch 
of long cilia on the right anterior area of the ventral surface. 
I saw no trace of the contractile vacuole in the living forms, 
but in most stained preparations a clear vacuole is present. 
The ciliated spores after a short free existence (about ten to 
fifteen minutes) settle down and begin to form a stalk 
(Pl. VIII, fig. 8). At this stage the whole animal becomes 
surrounded by a wall, the first trace of the theca, which is 
present, though not in so dense a condition, at a slightly 
later stage, even over the apical surface. In the fully deve- 
loped stalked form (Pl. VIII, fig. 9) the theca measures from 
‘043 to 08 mm. long by ‘03 mm. broad. The stalk measures 
from ‘02 to ‘03 mm. long, and is usually curved. In this 
stage the animal resembles very closely a form which was 
described many years ago by Robin, and which has not been 
seen since, Acinetopsis rara. Robin, in his account of 
this form, states that he only saw it three or four times in 
the midst of Acinetaria on stalks of Sertularia. He 
describes it in the following words : 
«C’est un animal long de 0:07 mm.—0:09 d’un tiers moins 
large, remplisant une goque ou theque en forme de verre a 
pied qui supporte un trés gréle pedoncle long d’un dixiéme 
de millimetre. 
“Corps uniformiment grenu, grisatre, avec une petite vesi- 
cule pulsatile, a surface libre plane, portant a son centre un 
tentacule et rétractile alternatement.” 
Robin himself stated that he knew nothing of the reproduc- 
tion of this form, and later observers seem to have been 
