MUSEUM OF COMPARATIVE ZOOLOGY. 327 
EXPLANATION OF THE PLATES. 
The appendages, from the first to the last pair, are indicated throughout by 
consecutive Roman numerals, They correspond with the appendages of the 
adult as follows : — 
J, first antenna. XI, third pair of legs. 
II, second antenna. XII, fourth “ ye 
IIT, mandible. Add IU eh " 
IV, first maxilla. XIV, first pair of abdominal appen- 
V, second maxilla. [dages. 
VI, first maxilliped. XV, second “ k "n 
VII, second maxilliped. Qi S ih p 
VIII, third maxilliped. XVII, fourth “ = E 
IX, first pair of legs (cheliferous). | XVIII, fifth F i " 
XA, second  * E XIX, sixth تس‎ m m 
The Arabic numerals denote the somites of the abdomen. 
ab, abdomen. ng, nerve-ganglion. 
ar, artery. 00, compound eye. 
cd, cephalic disk. 0 c l, ocellus. 
c p, carapace. re, external branch of appendages. 
ht, heart. ri, internal dd d 
4 n, intestine. rs, rostrum. 
lb, labrum. t, telson. 
m, mouth. vt, yelk. 
Plate I. 
Fig. 1. Egg with four segments produced by an equatorial and a meridional 
cleavage. Each segment contains a nucleolated nucleus (n), around 
which delicate lines of protoplasm are disposed like rays. 
Fig. 2. Egg with sixteen cleavage spheres. 
Fig. 3. The surface of the yelk is now divided into small polygonal blasto- 
meres. g, orifice of gastrula-cavity. 
Fig. 4. Profile view ot the embryo, four days after the gastrula-stage. The 
appendages have appeared from the first to the sixth pair. Except- 
ing the first, pair, they are bilobed or double. 
