694 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



Fiii. 14.— The fikst and second swimming legs 



OK A CHALIMUS OF ALEBION GLABER. 



joint and much larger than the endopod; both rami terminate in stout 

 spines, three on the exopod and two on the endopod, with several 

 smaller accessory ones on the outer margins. In the second legs the 



two rami are about the same 

 length, broad and disk-like, and 

 much shorter than the oblong basal 

 joint. They also terminate in stout 

 spines, live on each ramus. 



In the third legs (hg. 15) the rami 

 are almost exactly like those on 

 the second legs, but the basal joint 

 is very much swollen and has ol)- 

 tained a good start toward the 

 broad lamellar condition of the 

 adult. The exopod terminates in 

 five spines, considerably smaller 

 than those on the second legs, 

 while the endopod has only three. 

 There is no trace of the fourth 

 or fifth legs at this stage of de- 

 velopment. 



The young male is very similar to the female, except that the 

 carapace is relatively larger, while the free segments of the thorax 

 are much shorter and the segmentation is more distinct. 



The fourth legs (fig. 16) appear toward 

 the close of this chalimus stage, and are 

 distinctly bifurcate at the ends, the two 

 rami being very minute. At the next 

 molt the segment carrying them is fully 

 separated from those which follow it. 

 The posterior portion of the body noM' 

 rapidly elongates, and the larva advances 

 by several (4: or 5) molts toward its adult 

 form. The genital segment is separated 

 from the abdomen; at first smaller than 

 the latter, as in the Caliginte, it in- 

 creases until it becomes nuich larger. 

 The swimming legs also increase in 

 size, and the large apron of the third 

 pair becomes fully developed across the 



posterior end of the carapace, completing with the latter the large 

 sucking disk which is to constitute the chief organ of attachment to 

 the body of the host. At the same time the second antennae, which 

 have remained as organs of attachment through these early stages, 



15.— The third swimming leg ok a 

 chalimus of alebion glaber. 



