No: 3:] TUBULARIAN HYDROIDS. 425 
a hydranth at each end. But in these four fragments this 
heteromorphosis appeared more marked, as they were so short 
that the whole of the stem had been transformed into two 
hydranths, which were thus united without any stem portion 
between. When these double-headed forms were pressed out 
of the perisarc they presented various abnormalities ; in one 
case (Figs. 13 and 14) oral tentacles were found on each end, 
while in the center irregular-shaped tentacular buds were 
found ; while in another case (Figs. 18 and 19) the two com- 
plete hydranths were joined directly ; a flow of the somatic 
fluid from one to the other was readily seen. All these forms 
were in a vigorous state of activity; this was possibly one reason 
why they had not emerged from the perisarc in the usual way. 
This experiment showed conclusively that the regenerative 
power was zot limited to any particular regions of the stem, 
and at the same time it suggested the following experiment, in 
order to determine the limits of the regenerative power: 
(2) A second stem about 4 cm. was cut into fifty transverse 
sections, which were placed in water as usual. After two days 
they were examined, with the following interesting results: 
Twenty pieces were found with fully formed hydranths on one 
end; one with hydranths on each end; twenty other frag- 
ments showed abnormal regenerative forms, which had not 
emerged from the perisarc. A few typical abnormal forms 
may be described here. One was found (Figs. 15 and 16) 
which had the usual oral tentacles while coronal tentacles 
were lacking ; and in their place, at the other end, were 
found tentacle-like buds, and two fully developed tentacles 
projecting aborally. Another form (Fig. 17) was double- 
headed, but the number of coronal tentacles was complete on 
each hydranth. Still another form, found in a very small sec- 
tion, appeared to possess no definite form (Figs. 20-21), but 
was a rounded mass, with a row of knob-like tentacles on 
either side ; here evidently the stem was not long enough for 
even one hydranth. It was, however, in vigorous motion. In 
one case (Fig. e, 2) a very small fragment had become freed 
from the sides of the perisarc, and showed great contractile 
power while in it. 
