DEVELOPMENT OF E. SPINIFERA 303 



must be an abnormal specimen, for the rostral spine is usually strong in the last three 

 Furcilia stages. 



The shortest specimen of the present collection, 9-5 mm., differs from the others in 

 the following ways : (i) the frontal plate is square as in the last Furcilia ; (ii) the anten- 

 nular spine reaches more than halfway along the third segment of the peduncle ; (iii) the 

 antennular lappet is simple with a rounded margin ; (iv) there is no spine from the outer 

 distal corner of the second segment of the peduncle. The telson has two pairs of lateral 

 spines. Otherwise it resembles the seven specimens described below. 



In the seven larger specimens, io-o-ii-2 mm. long, the frontal plate is no longer of 

 the square larval form. For a short distance at the base of the plate the lateral margins 

 are roughly parallel ; beyond that they bend obliquely inwards — to make the distal part 

 of the plate triangular — by corners which are gently rounded in the five smaller speci- 

 mens, but sharply angular in the larger two. It is from these corners that the post-ocular 

 spines arise as in E. hngirostris. The margins of the frontal plate from the corners to the 

 base of the rostrum are denticulate. The rostrum reaches halfway, or more often more 

 than halfway, along the second peduncular segment of the antennule. 



The antennular spine varies from being as long to being half as long as the second 

 peduncular segment. The lappet is wide upstanding and incised, with two, three or more 

 points. There is a spine from the upper outer distal corner of the second segment of the 

 peduncle. The hepatic spines of the carapace are not present, but the projections de- 

 scribed in the largest specimen (below) can be seen to be developing. 



The free anterior margins of the tergal wings of the first abdominal somite may be 

 concave as in the adult. The third abdominal spine is as long as or longer than the fourth 

 somite ; very small spines are present on the fourth and fifth somites. The postero-lateral 

 spines of the sixth somite are present in some, absent as in the adult from others. The 

 telson has two to four pairs of lateral spines. 



In the largest specimen, 13 mm. long, the margins of the frontal plate are not 

 denticulate ; the post-ocular spines are present at its basal angles. The rostrum reaches 

 far along the second peduncular segment of the antennule. 



The lappet of the first, and the dorsal carina of the third, segment of the antennular 

 peduncle appear fully formed. 



The hepatic spines of the carapace are not yet formed, but there is on either side of 

 the carapace a large projection which is rounded off on all sides but the anterior where 

 there is a vertical face; from that the hepatic spine will arise (see Fig. 19 o, p. 225). 



The free anterior margins of the tergal wings of the first abdominal somite are con- 

 cave as in the adult. The third abdominal spine is nearly as long as the fourth somite ; 

 the fourth and fifth are very small. The sixth somite has no postero-lateral spines. 

 There are four pairs of lateral spines on the telson. 



