270 Black Currant Eelworm 



is suctorial in function. The anterior part of the pharynx contains 

 the spear, a thick chitinous perforated needle which is bounded 

 posteriorly by a distinct rim which is possibly trilobed. The spear 

 is protrusible and can be used as a spine for piercing the plant tissues 

 and as a tube through which the juices on which the animal feeds can 

 be sucked (PI. Ill, fig. 3). Posterior to the swelling the alimentary canal 

 passes back almost straight to the anus. At first it is narrow, and 

 may be termed an oesophagus, or it may be part of the chitinous 

 pharynx. Anyhow, this soon widens out into the intestine (PI. Ill, fig. 1). 

 All the above parts appear to be more or less muscular, and are con- 

 cerned with the inhibition of the plant's juices, and with the retraction 

 of the spear. The protraction muscles are a set running from the 

 rimmed base of the spear to the thickened chitinous areas around 

 the mouth (PL III, fig. 3). The walls of the intestinal part suggest no 

 muscular layer, but thicken and present an irregular almost lobular 

 condition outwardly, but a smooth and straighter margin internally 

 bounding the gut cavity. Nuclei can be seen here and there, but are 

 recognisable only with difficulty. They are small and spherical. The 

 walls contain alternately clear spaces, and parts dense with granules 

 which darken under the influence of the osmic acid and so probably 

 are of a fatty nature. The terminal part — ^or rectum — is devoid of 

 these granules, and the walls are thin. In the male the rectum opens 

 by the anus into the anterior end of a shallow cloacal depression. In 

 the female there is no distinct cloaca. 



The intestinal part of the alimentary canal is composed of com- 

 paratively few cells, and probably not more than two or three would 

 be seen in an ordinarily thin transverse section. 



The body wall. The cuticle which covers the body wall has already 

 been described. The cellular part of the body wall consists of a thin 

 layer of protoplasm in which nuclei lie arranged fairly regularly. In 

 stained specimens these nuclei are easily distinguishable from those 

 of the alimentary canal by their much larger size. On treatment 

 with Hermann's fluid the body wall nuclei are quite easily visible (PI. Ill, 

 fig. 6). The inner surface of the body wall bounding the body cavity is 

 uneven and is especially thickened just posterior to the suctorial bulb 

 where also it is composed of a protoplasm denser than elsewhere. 



In the male a thickening of the body wall occurs upon the ventral 

 surface of the tail, that is to say between the terminal point and the 

 posterior edge of the cloaca (PL III, fig. 7), It is probably a special 

 muscular development in connection with the wall of the cloaca to 



