BY J. P. HILL. 61 



the bulbs, while anteriorly it opens to the exterior beside one of 

 the bothridia. The hook fundaments have now become sejiarated 

 off from the cuticular wall of the proboscis and appear as short 

 inwardly-projecting processes with rounded ends. The.se by sub- 

 sequent elongation give rise to the long and slender hooks of the 

 adult scolex. The cellular strands in the bulbs are continuous 

 Avith vsimilar strands which run through the hinder parts of the 

 proboscis sheaths and become continuous with the proboscides 

 themselves. As development advances, well-marked obliquely- 

 crossing fibres are developed in the walls of the bulbs, which now 

 enclose large cavities. From the cellular strand the retractor 

 muscle is developed; anteriorly it is continuous with the proboscis, 

 while i)osteriorly it passes back to become inserted into the pos- 

 terior end of the cavity of the proboscis bulb. 



The blastocyst, when the scolex has reached the fully-formed 

 state, has an elongated club-shaped form, the largest found mea- 

 suring 14 mm. in length. The anterior club-shaped end contains 

 the scolex, attached by its posterior end to the bottom of the 

 invagination sac. Round its point of attachment a number of 

 minute hair-like processes of the cuticle are developed. The 

 .scolex is surrounded by a fluid containing granules and })robably 

 nutritive in function. As the scolex lies naturally in the invagi- 

 nation cavity, its parts liave the following disposition : the 

 posterior part lies in a line with the long axis of the l)lastocy.st ; 

 the neck curves round, forming a loop lying on the straight 

 posterior portion, while the head lies on one side. 



I append some notes from Linton's* description of the scolex as 

 explanatory of fig. 19, which is a drawing of the adult scolex freed 

 by mechanical means from the blastocyst : — The head is tetra- 

 gonal, transverse, cruciform. Bothria four, subcircular, convex, 

 cup-shaped, each the termination of a short cylindrical pedicel. 

 They are arranged in a cruciform manner, but also somewhat in 

 pairs, and capable of being directed either forwards or backwards 

 in pairs. Proboscides very long and slender, each one running 



• Loc. cit , " Notes on Eatozoa of Marine Fishes," p. 861. 



