144 Transactions of the Boyal Microseopical Society. 
there appeared, but not often, tiiough more so than in the case of 
the mouth, a dark round seam, which must be regarded as a 
sucker." This organ was more often noticed as an elHpse. He 
observes that the development of single animals was easier to 
trace than that of the threads from which it must be distinguished, 
and he gives a series of sketches showing how the germs in Fig. 3 
first became notched at one end ; how this increasing, forms a 
semi-lunar tail, the base of which thickens partially, constricts, and 
forms the two round swellings. The origin of the threads he did 
not succeed in tracing, but the paper contains many suggestions, 
comparisons with arthronema, &c. 
Afiother Bucephalus, B. Haimeanus, was described by Lacaze- 
Duthiers, in the 'Annales des Sciences Naturelles,'' 4°"® Serie, 
Tome 1. He found the abdominal glands of oysters and cockles 
completely invaded by the sporocysts of this parasite. " Eemoved 
from the organs," he says, " they unroll themselves to white fila- 
ments of great fragility, so that it is difiicult, almost impossible, to 
obtain them entire, and to examine their extremities. Their length 
is considerable, some being many centimetres. These long fila- 
ments, primitively cylindrical, are tubular. They become more 
or less moniliform in chaplets, through the contractions by which 
they are animated. The most perfectly developed animal found in 
the sporocysts presents, when first developed, the form of a 
flattened cone. At the top is seen a mouth surrounded with a 
cup-shaped sucker, and its base folds and filaments of variable 
lengths. The body is finely striated perpendicular to its axis. 
. . , . The mass is most transparent in the middle. We see in it 
a general cavity which must be considered as a single non-ramified 
digestive cavity, terminating with a cut de sac at the base, and 
communicating with the mouth at its summit. I observed nothing 
in its interior. The mouth is simple, without any hook. Above it 
is a conduit, contracted like an oesophagus, and communicating 
with the central cavity. In front it is surrounded with an 
expanded disk when the animal is elongated, and by a cup when 
the contractions are very strong. The walls of the body, from 
outside to in, are composed of three layers ; the outer one smooth 
and non-striated, the middle one becoming annulate under con- 
traction, and the inner one, which may be called parenchymatous, 
being the thickest." In this layer vesicles and granules were 
observed. "The extremity of the body which corresponds with 
the base of the cone bears a lamellar appendage, and two long 
filaments." These filaments are described as very contractile and 
extensile. The development of B. Haimeanus from a round germ 
through various gradations, is described and figured much like Von 
Baer's account of a similar development in B. polymorphus. 
