GAMMARIJS. 371 



and its diverticula are dark grey. The repro- 

 ductive organ of the left side, with its duct, is 

 shown to the side of the mid-gut, sheathed in 

 adipose tissue. The appendages are shown 

 in situ, but the first and second antenna? have 

 been cut short. 



Plate III. 



Fig. 1. Diagram showing the circulatory system. The 

 pericardial cavity, heart, arteries and efferent 

 vessels of the appendages are coloured pink. 

 The sternal sinus, with its afferent vessels to 

 the appendages, is coloured blue. The vessels 

 of the branchiae are shown cut short in the 

 first four thoracic segments, in the last three 

 they are omitted. The heart and the anterior 

 and posterior aortae are shaded to distinguish 

 them from the rest of the pericardial cavity, in 

 which they lie. The colouring is purely 

 arbitrary, and introduced for the sake of clear- 

 ness, since the blood is mixed throughout, 

 though the purest blood on the whole is that in 

 the pericardial cavity. The colouring, how- 

 ever, serves to show at a glance the sternal siuus 

 and pericardial cavity and the vessels respec- 

 tively related to these spaces. 



Fig. 2. An amoeboid corpuscle of the blood. 



Plate IV. 



Fig. 1. Diagram of a transverse section through the 

 body in the neighbourhood of the fourth seg- 

 ment of the thorax, showing the pericardial 



