28 G. O. Sars. 



dorsal part of the head, forming there a large rounded 

 mass, obtecting as a cap the foremost part of the 

 intestine, and consisting of numerous irregular, twisted 

 cæca. Interiorly, a distinct lateral branch is sent off from 

 each organ, extending to the ventral surface of the head in 

 front of the anterior lip, where it subdivides into a number 

 of rouuded lobules, This apparatus is also constructed in 

 essentially the same manner in the European Limnadia 

 lenticularis. 



The heart (see PL II, fig. 3; PI. V, fig. 3) likewise 

 agrees rather closely in structure with that in the above- 

 mentioned Phyllopod, forming a comparatively short tube 

 confined to the foremost part of the trunk, and extending 

 within the hind part of the cervical segment. It is some- 

 what wider in front than behind, and exhibits 4 pairs of 

 distinct venous ostia. 



Of the nervous system, the part occurring within the 

 head is not difficult to observe (see PI. Ill, fig. 1; PI. V, 

 fig. 4). The supra-æsophageal, or cephalic ganglion appears, 

 in a lateral view of the animal, as an opaque, somewhat 

 quadrangular body lying immediately behind the ocellus. 

 It is composed of 2 symmetrical halves confluent in the 

 middle, and sends off in front 2 juxtaposed, very strong 

 aud elongated nerve-stems, the optic nerves, which each 

 expand at the end into a claviform optic ganglion. From 

 this ganglion, numerous fine nerye-fibres are seen to originate, 

 entering the eyes and joining the several visual elements. 

 Interiorly the cephalic ganglion is produced on each side to 

 a conical prominence, from the tip of which issue the 

 nerves for the antennulæ. Just behind these prominences the 

 great oesophageal commissures are sent off, and from the 

 anterior part of these commissures the strong nerves for 



