20 FRANCIS H. WELCH. 
four hours’ steeping in hydrochloric or sulphuric acid produces 
no further result, while the same period of nitric acid com- 
pletely destroys every particle of the segment except the 
egg ; some of these, however, would seem to disappear under 
its influence, while others effectually resist it ; fire alone com- 
pletes their destruction. Hence I infer that the shell is com- 
posed of a chitinous material akin to the horn-like coverings 
of certain insects. ‘The embryo is spherical, with an oval 
offshoot occasionally to be seen from it suggestive of a head ; 
irregular folds can be discerned on its soft exterior, and six 
spicules arranged in a circle in pairs; these spicules are 
pointed at one end and thickened and globular at the 
other. 
Malformations.—Divergencies from the normal characters 
are not uncommon in these parasite colonies, the predomi- 
nating forms being,—a genital pit on each side of the seg- 
ment, a triangular shape of one segment from deficient 
development of one lateral half interposed between the 
usual square-shaped normal outline of segments above and 
below it. In one colony, in addition to the above monstrosi- 
ties, were segments with a double genital pit on the one 
side, and for about two inches of the colony there was no 
external infolding of the body structures to define the limits 
of each segment, nor was there any internal boundary, but 
the genital orifices were amassed on either side in patches of 
from two to five, and in total amount greatly in excess of 
what ought to have been present over this length of the 
parasite. 
In all these instances, whenever the genital pit was in 
existence, full developed internal structures corresponded to 
it. In those segments where the two genital orifices were on 
the same or opposite sides of the zooids, there was one uterine 
cavity, two vagine, aud two malesystems. In the triangular 
segment the components were normal in number, but the 
uterine canal was obliquely placed, the ovarian offshoots 
towards the base of the triangle, the lateral edge in which 
the genital pit was seated, were as usual, those on the oppo- 
site side were undeveloped. In the portion of colony 
above mentioned with so extraordinary an amount and _ posi- 
tion of genital pits, there the uterine canal extended through- 
out the malformed part with frequent vagine and spermatic 
tubes, full developed ova in the channels and glands. ‘These 
malformations exhibited either excessive or arrested develop- 
ment. The uterine canal was in accord with the bedy 
structures, exhibiting no segmental division where the 
differentiation was not complete as regards the inflected skin 
