EPIZOA. 



151 



These ovisacs singularly resemble the seed-capsules of certain 

 plants, especially the Cassia fistula^ being divided into a series of 

 cells or chambers by transverse septa, placed at regular distances. 

 Each cell contains an elliptical or lenticular ovum. 



Two slender white filaments (^, ^) running almost parallel with, but 

 at a distance from, each other, through the whole length of the under 

 surface of the abdomen, nearer the margins than the middle line, form 

 the chief and most conspicuous part of the nervous system. 



The most common mechanism of adhesion in the Epizoa is a cir- 

 cular sucker, developed upon the confluent extremities of a pair of 

 obscurely jointed tubular feet, as in this Lerneopoda of the Shark *, 

 in the Achtheres of the Perch {fig. 81.), the Tracheliastes of the 

 Chub, <Src. In the last-named parasite, which may be found adhering 

 to the fins of the Chub in the months of October and November, the 

 head and thorax are confluent, unless the segment to which the bases 

 of the before-mentioned feet are attached be held to represent the 

 thorax. The abdomen isj as usual, the largest segment. The mouth 

 {fig. 80. «) is a circular aperture, fringed with minute short bristles ; 

 on each side there is a maxilla (e) dentated at the inner margin, and 



terminated by a bifid hook. The 

 antennae (/) are represented by 

 two short lancet-shaped processes 

 terminated at the apex by a few 

 extremely short bristles. The most 

 conspicuous appendages of the head 

 are, however, a pair of mandibles 

 (6), which consist of two obscure 

 joints, the second of which has a 

 bifid extremity ; the outer division 

 (c) is armed by a strong curved 

 spine, which is opposed to two 

 short straight spines; the inner 

 division (d) is tipped with four 

 small spines. Immediately behind 

 the large tubular prehensile pro- 

 cess is a short rudimental extremity, supporting a moveable hook, 

 which is opposed, as in the mandibles, by two short spines. The 

 muscular system is sufficiently conspicuous in the head of this Epizoon 

 in the form of distinct fasciculi of fine fibres (^.) 



In this Penella\ the head resembles a cauliflower, swelling out into a 

 globose group of slightly branched and obtuse wart-like processes, 



Tracheliastes. 



* No. 286. A. 



t No. 286. 



L 4 



