88 Memoirs of the Indian Museum. [Voi,. I, 



separated from one another, each one running in the groove between adjacent rows 

 of ceUs." 



Thus we see that in Oniscus there is a considerable difference between the 

 anterior and posterior parts of the mid gut. This differentiation of the mid gut into 

 two parts, and the paraboHc arrangement of the cells in the posterior half, may be 

 regarded as foreshadowing the organisation of the intestine in Bathynomus. In other 

 words, it is probable that the organs herein described as the mid and hind gut of 

 Bathynomus, which are completely different in the structure of their walls and are as 

 separate from one another, both in degree and kind of separation, as the uterus and 

 vagina of a mammal are separate, are together homologous with the extensive mid 

 gut of the smaller Isopods ; for we can see at least in some small Isopods such as 

 Oniscus a distinct indication of division of the mid gut into two parts. 



Minute Structure of the Hep atop ancreas. 



In the structure of this organ the genus differs remarkably from all other Isopods 

 so far as they are known. As previously mentioned, this difference in the structure of 

 the organ seems to be a necessary resrdt of the large size of its possessor. 



A transverse section of one of the six lobes shows that it is composed of a number 

 of short tubules, radiating from the central axis of the organ. Some of these tubules 

 are simple, and lie in a straight line between the centre and periphery of the organ, 

 others branch dichotomously and are somewhat contorted. Figure i (pi. xii), which 

 is a photograph of a thick unstained section cleared and mounted in balsam, shows 

 the character of these tubules. On referring to this figure it will be seen that the 

 separate tubules are clearly defined by a blotched, wavy, dark line, which is due to 

 the presence of certain peculiar contents of the cells composing the tubules. In 

 proximity to the nucleus of each cell are numerous yellow granules, which in the 

 aggregate form a dark brown mass. The united presence of these granules has 

 marked out the limits of the tubules; while the protoplasm and nuclei, being un- 

 stained, have been rendered almost invisible by the medium in which the section is 

 mounted. Figures i and 3 show clearly that the hepatopancreas of Bathynomus is a 

 racemose gland of primitive type. 



Figure 2 is a photograph of a thin stained section, cut transversely through a 

 single component tubule. It is not unlike a transverse section of one of the four 

 simple unbranched tubes which compose the hepatopancreas of a small Isopod. It is 

 composed of about twenty rows of large conical cells the apices of which protrude into 

 the lumen. Towards the base of each cell is a large oval nucleus measuring as much 

 as -05 mm. Grouped round this nucleus is a mass of coarse granules, which take the 

 stain with such avidity that they appear almost black in sections stained with hsema- 

 toxylin. These are the granules which, unstained, have a yellowish brown colour. 

 Towards the apex of the cells the protoplasm shows large circular vacuoles, from 

 which their contents have been dissolved. In the reticulum between the vacuoles 

 fine granules can be seen. 



Perhaps owing to the large size of its constituent cells the hepatopancreas of the 



