of the Fishery Board for Scotland. 



77 



Fourth Pbreiopod, 5per., figs. 42, 52, and 45. 



The enclopodite shows five joints. On the propodite the spines have 

 very large serrations on their distal halves, and smaller teeth on their 

 proximal halves. On the other side the spines have small serrations. 

 There are two kinds of serration on the long spine of the dactylopodite. 

 At the base of this spine there is a tooth on the dactylopodite. 



The exopodite had 24 (26) setse. 



Four gills and one epipodite are connected with this limb. 



Fifth Pereiopod, 5per., figs. 42, 52, and 45. 



On the endopodite there is a little tooth at the base of the terminal 

 spine. 



The exopodite had 22 setse. 



One gill, a pleurobranch, is connected with the fifth pereiopod. 



Branchle. 



The number and the arrangement of the gills of the first stage zoea 

 are similar to the condition in the adult. Two of the gills, however, are 

 here rudimentary. In fig. 49, pi. ii., the branchial cavity is shown. 

 The gills are represented in the positions they occupy, but are shown 

 much more slender than they actually would appear. They are packed 

 close together. The division, of the gills into podobranchiae, arthro- 

 branchise, and pleurobranchise is clearly shown in the case of the majority 

 of the gills, but some there are which, from their position, might be 

 regarded as pleurobranchs. In the adult, however, they are arthro- 

 branchs, and very probably are arthrobranchs in the larva. They are 

 the gills on the top row of the arthrobranchs in the following scheme. 

 The Table exhibits the arrangement of the gills in the first zoea stage 

 (vide fig. 49). The gills are arranged in the branchial chamber in four 

 rows. The highest row consists of four pleurobranchs belonging to the 

 second to fourth pereiopods. The next row consists of five arthrobranchs 

 which are connected with the third maxillipede and first four pereiopods. 

 The third row comprises another set of five arthrobranchs attached to 

 the same appendages. The fourth row includes six prodobranchs, borne 

 by the second and third maxillipedes and the first four pereiopods. The 

 first and last of the series are rudimentary gills. Each of the above- 

 mentioned appendages, with the exception of the fifth pereiopod, has an 

 epipodite. On the coxopodite of the last pereiopod there is a small process 

 which may represent the epipodite. 



Herrick says that in the American lobster there is no rudimentary gill 

 attached to the second maxillipede. 



In Fig. 49 the following letters are used : — pl.-br., Pleurobranch ; 

 ar.-hr., Arthrobranch ; pd.-br., Podobranch. 



[Table. 



