LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 64.7 
small numbers of mature cercariz# were forced out in the 
stream of water from the exhalent siphon. These cercariz 
swam actively for about two hours and then sank to the 
bottom. 
By the addition of diatoms the water was kept fresh, and 
the cercariz thus kept under observation for several days. 
During this time the tails were broken off, but the cercariz 
were still capable of making slow progress on the bottom of 
the dish by means of contractions of the body. 
At the end of four days all were dead. None encysted 
themselves, and in none were any changes of structure to be 
seen. 
THe Sporocyst. 
The youngest sporocysts that I have been able to identify 
positively as such, consist of a central, irregular, sac-lke 
body from which one or more cylindrical branches are 
given off (figs. 2 and 3), the structure being not unlike the 
sporocysts of Leucochloridum which Heckert (39, 1889) 
has described. ‘The cylindrical branches are the germ- 
tubes, and it is from these and from similar new branches 
of the central body that the great mass of fibres found in the 
badly-infected oyster is derived. The tubes grow to alength 
of several centimetres, repeatedly branching throughout their 
course. In branching many strange effects are produced, to 
some of which may be due Pagenstecher’s (25) idea that the 
tails of the cercariz give rise to new germ-tubes. Fig. 5 
shows an appearance which at first sight might give such an 
impression. A further discussion of this point will be given 
later. 
The germ-tubes are usually of a rather uniform diameter 
(01 mm.; fig. 4). In some instances portions of the tube 
become enlarged and form conspicuous sac-like swellings in 
which a considerable number of cercariz may be found 
(fiz. 3). 
The growing end of the tube is rounded and of a somewhat 
greater diameter than the older portion (fig. 4). 
