of the Fishery Board for Scotland. 



73 



following the scent dispersed by the current of water flowing through the 

 box. 



One little lobster took up its abode for a day or two in a Purpura 

 shell which lay on the sand that covered the bottom of the aquarium, 

 but when it attracted attention, it had excavated in the sand a hole 

 below the shell, and in it it lay. The hole was deep to the front, and 

 was a neat fit. The lobster pushed out a quantity of sand, two armsfull, 

 in front of it, and removed larger grains of sand and a little piece of 

 debris with its maxillipedes. When returning from a promenade round 

 its prison it carefully tested its lair before it backed into it. It was alone 

 in the aquarium. Now this lobster did not imitate an adult or any other 

 young lobster in taking up its abode in the shell, or in digging a cave in 

 the sand. When food was tumbled in it seemed to resent its approach. 

 It appeared to be attracted by the scent at first, and then it put some fresh 

 mussel that tumbled into its cavity out of the hole, while some mussel 

 that was apparently old was left in. It was noticed that the mussel stuck 

 to the pereiopods. 



Another little lobster, in its wandering about among the sand and mud, 

 got its pereiopods and maxillipedes covered with fine debris which, no 

 doubt, consisted, in considerable part, of diatoms. It was observed to 

 pick off the debris and put it into its mouth. Sometimes the mud in 

 the aquarium was all punctuated as if it had been probed all over with 

 the legs of the lobster. 



The Larval Stages. 



In the lobster the zoea is a much more specialised organism than in 

 certain of the other decapod Crustacea, e.g. Crangon and Carcinus. One 

 important respect in which the former differs from the two latter is in 

 the possession of functional gills. The presence of the gills determines 

 the form of the appendages concerned in the respiratory function, viz. 

 the second maxilla, and the maxillipedes which are employed in securing 

 a circulation of water through the branchial chamber. The gills and 

 their arrangement being very nearly similar to the condition in the 

 adult, it follows that the function of the appendages is that which they 

 perform in the adult, and their form is therefore practically that of the 

 adult. In Crangon and Carcinus the maxillipedes have no respiratory 

 function to perform in the zoea ; they and the second maxilla are in form 

 quite dissimilar from the adult condition. The adult form of these 

 appendages are similar but not identical in the lobster and Crangon. 



The stages which will now be described have not been determined by 

 following a lobster in its successive moults. They have been dis- 

 criminated from the general collection of larvaa which were developing 

 in the hatchery. In the case of the higher stages, e.g. last zoea stage, 

 megalops, first and second young stages, the casts connecting adjacent 

 stages were observed. 



During the research it was found necessary to redissect this form 

 which has already been treated by Sars and others, while the American 

 species has been worked out by Smith and Herrick in elaborate detail, and 

 profusion of drawings. 



The drawing in the present case represents the condition found in the 

 appendage examined. The opportunity did not occur to dissect several 

 zoese of the same stage with a view to determine the variation in each 

 limb, and from that to fix the normal condition. When a comparison 

 has been instituted between the limbs of different zoese, variation in the 

 hair arrangement, and in the nature of the hairs themselves, has been 

 noted. 



