On Bucephalus polymorphus. By H. J. Slack. 143 
ment. Chiefly in the liver and region of the kidneys, he discovered 
a number of white " threads," similar to what he had noticed two 
years earlier. They were easily removed by a needle, and he was 
at first doubtful whether they were worms, or lymphatic vessels. 
Fig. 2 represents one of these thread-like objects in its natural size, 
" seen on the dark ground of the kidney, and lying just under its 
enveloping membrane." He found it exceedingly difficult, if not 
impossible, to dissect out one of these hair-like bodies when buried 
in the substance of the organ. Fig. 3 shows an instance in which 
he was successful, x 20. Further search led to the discovery of 
dichotomously-branched threads, " which called to mind the lower 
vegetable forms," and which he named SeMeimfdden, protoplasm- 
threads. Fig. 3 exhibits a stage of development, the simple thread 
being constricted at various points. Fig. 4, the same in more de- 
veloped condition. " The elongated swellings are further developed 
than the round ones." The small objects to the right of Fig. 3 are 
the germ-cells the swollen parts contain. Fig. 4 represents several 
forms branching from one stem. " In the most developed parts the 
naked eye is able to see that these are no longer germ-cells, but 
developed animals." 
" The shape of the creature," says Yon Baer, " which lives in 
the swellings of the threads is most wonderful. I twice saw it," 
he exclaims, "under strong magnification, audit seemed as if the 
head of an ox was before me, with the horns directed towards me." 
" The horns, or rather arms, were formed of soft matter, curved 
and conical, and their bases were seated upon two pudding -like 
bodies (Wiilsten). Their tips were rounded, and at times showed a 
fine projecting transparent point, which seemed capable of being 
thrust in and out. The 'horns' at times curled like those of a 
goat, and fell off." At other times their contents separated into dis- 
tinct masses, as in Fig. 5. In some cases the arms took the aspect 
of chaplets of pearls, and swam swiftly away. In others, after 
separation, the little balls into which the contents were resolved 
fell out. How long the " pearl chaplets " lived. Yon Baer could not- 
discover ; but they did not die quickly, and he noticed their lively 
motions for a good half hour. 
The older the creature was the larger and darker he found the 
two pudding-like swellings, but they were usually lighter than the 
horns. At times they looked as if full of germs. 
" The body is less changeable in shape than the other parts. 
It is flat, now lancet-shaped, now slightly drawn in in the middle, 
and sometimes strongly indented on one side. The connection 
with the two round bodies was at times very narrow, at others 
broader ; but this may have been the effect of position rather than 
of structure .... a mouth opening is usually invisible." When 
seen it appeared as in Fig. 1. "In the middle of the body 
M 2 
