14. Mandible of the same, The palpus has been removed. ¢, tendon of the mandibular muscle, 
15. Mandibular palpus of the same. 
16. Second maxilla of the same. 
17. First maxilliped of the same, with endopodite (77), exopodite (7 ¢), and epipodite. 
18. Second maxilliped of the same. 
19. Third maxilliped of the same. 7, gills. 
20. Proximal end of left cheliped of the same, furnished with a stout hook. Seen from ventral side. 
21. Proximal end of left leg of the second pair, with two hooks, seen from ventral side. From the same stage. 
22. One of the three long curved sete on the terminal segment of the last pair of legs of the same (see fig. 12). 
The other two sete are destitute of the teeth with which this one is furnished. 
23. One of the abdominal limbs of the same. The endopodite is provided with hooked sete (7), which serve to 
lock together the abdominal limbs of the two sides. 
24. Posterior abdominal appendage. No endopodite. 
25. The megalopa represented by fig. 12 passes by a single moult into the crab stage of the form represented in 
this figure, dorsal view. The eyes are much larger than in the adult, the antenne longer, and the length 
of the carapace much greater in proportion to its breadth, and of very different outline. Breadth of cara- 
pace, 4mm. 
26. The same, ventral view. The form of the abdomen would seem to indicate that this specimen is a young 
male. The third, fourth, and fifth abdominal segments, which, in the adult male, are fused together, are 
still free. 
27. Carapace of adult Cancer borealis, half natural size. The megalopa and young crab represented in figs. 12, 25, 
and 26 belong either to this species or to the closely allied C. irroratus. This figure is introduced to show 
the marked difference in proportions and outline between the young and adult stages. Drawn on stone, 
from nature, by A. Meisel. 
28-30. Young stages of Pinnixa (Sayana?) from Newport, R. 1. From Faxon, On some Young Stages in the 
Development of Hippa, Porcellana, and Pinnixa, Pl. 1V., V. Bull. Mus. Comp. Zodl., V., 1879. 
28. Last zoéa stage, seen from above and in front. ab, penultimate abdominal segment, produced on each side 
into a rounded lobe. Through the transparent carapace are seen the rudimentary and as yet functionless 
ambulatory appendages. The cross denotes the natural size. 
29. The third maxilliped and five ambulatory limbs removed from the body. VIII, endopodite of third 
maxilliped. VIII’, exopodite of third maxilliped. VIII", epipodite of third maxilliped. 
80. The zoéa (fig. 28) passes directly, at one moult, into the adult form shown in fig. 30. This abbreviation of 
the developmental history whereby the megalopa stage is eliminated is very unusual among the marine 
Brachyura which leave the egg in the zoéa form. S. I. Smith has shown that another species of Pinnixa 
passes through a megalopa stage. Some land-erabs, as has long been known, leave the egg in the adult 
form, like Astacus among the Macrowra. 
