170 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



1. The gastrolith is not present. 



2. Calcifications of the stomach wall are entirely lacking and the 

 gastric "ossicles" are formed entirely by thickenings of chitin. 



3. The dorsal cardiac plate is covered internally with sparsely 

 arranged pairs of slender bristles and extends laterally over a large 

 part of the areas on the sides of the stomach occupied in the adult 

 by the gastroliths. 



4. The gastric mill differs more or less fundamentally from that 

 of the adult. 



The upper and lower cardiac canals, the cardio-pyloric valve, the 

 lower pyloric canal, and the pyloric valves, which are the most essen- 

 tial structures of the stomach, retain through all stages the same form 

 and relationship. 



The Stomach of the Third-Stage Lobster. (Plate VII, Fig. 11.) 



The stomach of the third-stage lobster is the first of the series in 

 which the gastric mill appears. The median tooth is comparatively 

 small ,and ends in a round median knob and a pair of lateral cusps 

 which remind one of the bilobed form of the median tooth of Astacus. 

 The anterior dorsal and posterior do.'sal pads are united in a single 

 large lateral pad covered with backwardly directed bristles. The 

 lateral tooth appears with its accessory cusp and with the general 

 form of the adult tooth. The infero-lateral tooth is also present 

 and has one large and one small cusp. The middle and lower 

 cardiac pads have the same form as in the adult. 



The ventral surface of the cardiac sac of the stomach of this, and 

 also of the first, second, and fourth-stage lobsters, unlike that of the 

 adult, is covered with small brushes of bristles. The simplest of 

 these (Plate V, Fig. 5 A) consists of two parallel bristles, and the more 

 complete brushes have three, four, or more bristles which are inserted 

 upon a slightly crescentic ridge. The bristles which separate the 

 upper and lower cardiac canals in the stomach of this and of the first 

 and second stages are round and are not plumose. The cardio- 



