154 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
tain strongly refractive, yellowish globules. These larvae are pho¬ 
totactic, though to a less degree than Brachyuran zoeae, and in a 
glass vessel range themselves head downwards against the lighted 
side. They swim tail foremost, and rather slowly and steadily. 
The surfaces of the body, however, are not definitely oriented, 
though either the dorsal or ventral are uppermost more frequently 
than the lateral. This lack of orientation seems to be correlated 
with the complete absence of otocysts in the three earlier stages and 
with the undeveloped condition of these organs in the fourth stage 
or metazoea. While swimming, the eyes, antennae, and uropods 
are invariably held in the positions shown in figure 4 (plate 4). 
In captivity, the moults between the successive stages usually 
take place at night or in the early morning, and the larvae sink to 
the bottom of the aquarium and remain quiescent for a considerable 
period previous to the actual ecdysis. The manner of moulting 
under natural conditions could not be determined. 
The length of the zoea phase and of its several stages is not 
known. The occurrence of the successive stages in the auftrieb 
indicates that the phase possibly extends through only two or three 
weeks. But little reliance, however, can be placed upon data of 
this class, and it is very probable that the period varies with the 
external conditions, as is the case with other crustacean larvae. 
In our Eupagurids, the zoea phase comprises four stages, which 
may be separated as follows : — 
First Zoea. 
Third maxilliped rudimentary (pi. 4, fig. 1) ; sixth abdominal 
segment not distinct from telson; exopods of maxillipeds 
with four feathered setae; thoracic limbs as a simple mass of 
undifferentiated tissue. Length, 1.9-2.7 mm. 1 
Second Zoea. 
Exopod of third maxilliped functional as swimming-foot; 
endopod barely indicated (pi. 6, fig. 14 2 ); exopods of maxil¬ 
lipeds with six setae; anlagen of nropods as a band of tissue 
along each side of the telson (pi. 7, fig. 31 2 ); thoracic limbs 
distinct, rudimentary, fourth pair excessively long, fifth pair 
short and concealed beneath others (these proportions are 
found also in the two following stages). Length, 2.7-8 mm. 1 
1 Including as they do the larvae of two species, all the measurements have 
an unduly extended range. 
