ECHINOKHYNCHUS. 149 



boscis around the oesophagus*; two other muscles, b b, antagonistic to 

 the former, arise near the spines themselves ; and these, aided by the 

 contractions of the walls of the body, are the agents by which the pro- 

 trusion of the head is effected. Although the teeth or spines which 

 render this organ so formidable are merely epidermic appendages, they 

 are raised or depressed at the will of the creature ; and it is therefore 

 probable that, minute as they are, they have muscular fibres connected 

 with them, serving for their independent motions. These spines, more- 

 over, are not always confined to the head, but in many acanthocephalic 

 worms are found on various parts of the body, wherever their office as 

 instruments of attachment is by circumstances rendered needful. 



(392.) The digestive system of the Echinorhynchus is extremely 

 simple. The mouth is a minute pore, placed at the extremity of the pro- 

 boscis, which communicates with two slender canals, //, at first of great 

 tenuity, but near the middle of the body assuming something of a saccu- 

 lated appearance. Towards the tail these vessels gradually diminish in 

 size, until they are no longer distinguishable ; but they have not been 

 seen to give off any branches, or to communicate with each other. 



(393.) Near the origin of these nutrient tubes are two large casca, 

 nearly an inch in length, called lemnisci (fig. 74, 1 & 2, d d), which are 

 probably connected with the digestive function. 



(394.) The female Echinorhynchus, as is usually the case in Dioe- 

 cious Entozoa, is considerably larger than the male, as may be seen in the 

 figure. In the former (fig. 74, l), the ovary, c, is a capacious organ, 

 occupying the centre of the body, and extending along its entire length. 

 When minutely examined, it is found to consist of two compartments, 

 or distinct sacs, one occupying the dorsal, the other the ventral aspect 

 the two tubes being separated by a septum. The dorsal ovary com- 

 mences near the tail, at g, by a cul-de-sac, and, enlarging as it runs 

 forwards, terminates near the point, c, by uniting with the ventral por- 

 tion. The anterior part of the canal, b, is common to both divisions of 

 the ovary ; and from this the ventral tube runs backwards to the pos- 

 terior end of the body, where it terminates in a narrow duct, which 

 opens externally at h. It would seem, therefore, that the last-men- 

 tioned opening is the only excretory passage from the ovarium, the 

 connexion apparent in the figure, between the common sac, b, and the 

 root of the proboscis, being merely of a ligamentous character. 



(395.) In the female of some of the Acanthocephali, according to 

 Sieboldf, there are neither proper ovaries nor a uterus, but in their 

 place are found numerous oval or round flattened bodies of considerable 

 size, which float freely in the anterior of the cavity of the body ; they 

 have regularly- defined borders, and are composed of a vesicular, gra- 

 nular substance ; in these the eggs seem to be formed, so that they may 



* These muscles are seen of their natural size in fig. 74, 1 , at e c. 

 t Siebold and Stannius, Comp. Anat. p. 124. 



