ON AMPHILINA PARAGONOPORA 79 



a modian papilla in the bay open the ductus ojaculatoriiis 

 (at the extremity of the papilla in the middle line), vagina 

 (at the base of the papilla on its dorsal side, the opening thus 

 being practically terminal) and terminal excretory duct (imme- 

 diately to the left of the opening of the ductus and sometimes 

 confluent with it). The parasites when mature (the uterus 

 being tilled with larvae in various stages of development) 

 apparently escape from the fish by boring through the l)ody- 

 wall at the base of one of the pectoral fins. In addition to 

 the ' active ' parasite, an inactive stage in its life-cycle is to be 

 found in the form of irregularly shaped masses usually attached 

 to the mesentery. 



2. The general plan of the reproductive system is similar 

 to that in Amphilina foliacea, but there are some note- 

 worthy differences, already summarized at the end of Part I. 



3. The small boring proboscis (covered with a serrated 

 cuticle) is connected with and manipulated by a huge boring 

 muscle (formerly miscalled ' retractor ' by some authors, 

 and by others interpreted as a bundle of gland ducts — the 

 ' problematic ' cells of Salensky being the glands) which is very 

 thick anteriorly and extends posteriorly, though in an 

 attenuated form, to the region of the ovary. The fibres of this 

 boring muscle end in the giant cells which Salensky called 

 ' problematic ' and which I have renamed ' anchor '-cells. 

 The function of the 1)oring muscle is (1) to give a semi-rotary 

 movement to the proboscis (its fibres being twisted anteriorly), 

 (2) to act as a stout support for the anterior end of the body 

 when engaged in boring, and (o) to drag the hinder portion of the 

 body through the perforation made by the proboscis — and these 

 three functions account for the enormous size of the muscle. 

 A true and distinct retractor muscle lies externally to the boring 

 muscle. 



4. The excretory system consists of two lateral main channels 

 which unite posteriorly and form a short straight terminal 

 excretory duct which opens in the median line posteriorly, 

 and a series of smaller loops and branches given off from these 

 two lateral main channels, which appear to form, typically, 

 three series of ' rings ' when the body is viewed end-on (PI. '3, 

 fig. 6). Flame-cells are absent. 



5. The central nervous system is, in the main, that described 

 by Lang for Amphilina foliacea. 



6. Some stages in the development of the larva are described, 

 and the larvae, when liberated from the uterus, appear to be 

 similar to those of Amphilina foliacea. Fully grown 



