36 Mr.G. Hodge on the Development of a Species of Pycnogon. 
The natural inference on first finding these sacs would be that 
they had been attached by the mature Pyenogon—in fact, were 
the germs cemented to the polypary, and that the difference in 
form (pear-shaped, instead of globular as when attached to the 
false feet of the female) might be the result of growth. On 
submitting, however, the sacs to microscopical examination, their 
external appearance so closely resembled the growth of Coryne, 
and, on the other hand, was so totally different from anything 
that could be imagined to be the product of a Pycnogon, that. 
little doubt remained on my mind that the sacs were really the 
result of some peculiarly directed growth of this zoophyte. To 
ascertain, therefore, how far the cavity of the sac communicated 
with the central portion or ccenosare of the Coryne, a sac was 
cut transversely, near to its connexion with the supporting stem ; 
and a gentle pressure being applied, the nutrient matter of the 
Coryne escaped from the wound, just as would be seen if a stem 
was so cut. ‘Transparent specimens were next examined, and 
the result left no doubt of the sacs being part and parcel of the 
Coryne. All question upon the matter was, however, completely 
set at rest by my finding that these sacs had been already noticed 
by Prof. Allman, who, in a communication made to the British 
Association in 1859, arrived at a preéisely similar conclusion 
with respect to their zoophytic origin. The abstract of his 
paper, being very short, may be here quoted entire. 
“* On a remarkable form of Parasitism among the Pycnogonide. 
“ By Professor ALtman, M.D., F.R.S. 
“The author described the occurrence, on the branches of some 
species of Coryne, of peculiar pyriform vesicles, which might at first 
sight be easily taken for the reproductive sacs of the Zoophyte. 
They had their cavity in free communication with the general cceno- 
sareal cavity of the Zoophyte ; and an endoderm, ectoderm, and - 
external chitinous investment were easily demonstrable in their walls. 
The nature of their contents, however, at once distinguished them 
from the proper reproductive sacs of the Coryne; for in every in- 
stance they enclosed a Pycnogonidan (Ammothea’?). The enclosed 
Pycnogonidan was always solitary, and in the smaller vesicles was 
still embryonic, while in the larger ones it presented an advanced 
stage of development, and was ready to escape from its confinement 
by the rupture of the surrounding walls.” 
Now come the questions :—How is the sac formed, and how 
does the young Pycnogon get into the sac? These problems 
are more difficult to solve than would at first appear; yet it may, 
I think, be proved that at any rate the sacs are merely modified 
growths of the Zoophyte. 
If figs. 6, 7, 8, & 9, Pl. IV. are examined, it will be seen that 
