8 



General Morphology. 



latter to the abdomen of the host; the method of communication between the root system and 



the external portion of the body is shown in transverse section on Piate 6 fig. 6, which passes 



through the chitinous ring: the tissues of the host are distinguished by the red tint. 



4 The external sac-like portion of a Peltogaster with which we are now concerned is of 



a vivid red colour and of an irregular cylindrical shape (Piate 1 fig. 8); anatomically it con- 

 ti, _ 

 sists of two chief parts: an external mantle, which surrounds a visceral mass. 



Vi.SC 



7nc 



m 



-TOC 



Text fig. 1. 



As seen in the diagrammata transverse section (Text fig. 1) between the mantle (m) 

 and the visceral mass (viso) there is a cavity, the mantle cavity or brood pouch (me): this 

 cavity extends ali round the visceral mass, except along the surface apposed to the abdomen 

 of the host; here the visceral mass is broadly attached to the mantle cavity by means of a 

 mesentery (mes) which runs in the long axis of the body, and is pierced in the centre by 

 the ring of attachment (ring). The mantle externally and the whole of the mantle cavity 

 internally is lined with chitin (coloured red in diagram); the mantle is provided with circular 

 and longitudinal muscles, and so also is the visceral mass. 



Besides the muscular and connective tissues of the mantle and visceral mass, Peltogaster 

 is provided with several organs, the relative positions of which are of great importance. 



At the end of the body pointing to the head of the host is the mantle opening (op\ 

 often misnamed the cloaca; this opening, which serves for the aeration of the brood pouch and 

 for the emission of the Nauplius young, is provided with a sphincter muscle, and its lower 

 lip is attached to an extremity of the mesentery. In the diagrammatic longitudinal section of 

 Peltogaster shown in Text figure 2, the mantle opening is seen (op), the mesentery (mes) is 

 indicated by the horizontal lines at the base of the figure, and at the junction of mesentery and 

 visceral mass are shown the nervous ganglion (gn), and the openings of the oviduct (ovd) 



