ON PENNELLA BALZINOPTERZ. 413 
like antennee, relics of the free Cyclops stage of development, such as are represented 
by Koren and DantexssEn in their figure 9, tab. xvi. 
From the base of the head three horn-like arms arose, which extended almost 
horizontally outwards ; they were the anchors of attachment implanted in the blubber 
of the whale. One sprang from the mesial dorsal surface, whilst the others were right 
and left lateral. They varied in length in the same specimen, and the dorsal arm was 
usually the shortest. They differed also in thickness and were irregular on the surface ; 
the free end was blunt (Plate I. figs. 1, 2), and in one specimen a lateral arm was 
bifurcated. 
The body of the parasite extended from the base of attachment of the arms to the 
free end of the pennated portion. It varied materially in thickness in different parts 
of its length. Immediately below the arms its transverse diameter was 3 to 4 mm. ; 
it was somewhat flattened on both dorsal and ventral surfaces, and on the ventral 
surface, close to the mesial line, most of the specimens showed pairs of appendages. 
They were so minute as to be scarcely visible to the naked eye. In two specimens 
four pairs were seen, as had been figured by Koren and Dantutssen. In others, two 
pairs, or even a single pair, only were recognised, and in a few they were not visible. 
Their recognition was assisted by the presence of a spot of dark pigment. Four is 
without doubt the typical number of these feet-like appendages, though it would seem 
as if this number was not always preserved in the process of transformation from the 
embryonic cyclopoid form to their retrograde condition in the adult (Plate I. fig. 2). 
Hight mm. from the base of the arms the transverse diameter of the body diminished 
to 1°5 mm., and fora considerable distance it preserved this diameter ; it was cylindrical 
in shape, smooth on the surface, and not unlike in form and colour a steel knitting- 
needle. It was an elongated neck-like division of the body, very characteristic of the 
parasite, and may be regarded as the thoracic segment. 
The body was prolonged into the abdomen, which increased in bulk, measured 
4 mm. in breadth, lost its smooth appearance, and was marked by numerous transverse 
constrictions, between which minute bead-like projections were arranged in rows. 
The abdomen was the widest and most deeply coloured part of the body; as it con- 
tained both alimentary canal and the female genital organs, it may appropriately be 
named the genito-abdominal segment. At the lower end two genital openings were 
seen on the ventral surface, from which depended the pair of ova strings. Immediately 
above these openings was a small rounded eminence, to which probably the male 
parasite may attach itself when engaged in impregnation. 
The ova strings were a pair of very slender threads, yellowish-brown in colour, and 
of remarkable length ; in one parasite each string measured 400 mm. (15°7 in.). They 
floated free in the surrounding medium; they were sometimes almost straight, but at 
others they had an undulating character. 
The terminal part of the body was prolonged behind the genital openings from 25 
to 30 mm., varying in the different specimens ; it was only 2 mm. in transverse diameter 
