THE EURYPTERIDA OF NEW YORK 121 
In the primitive trilobite Harpes the ocelli remain functional through 
life and no compound eyes are developed; we may infer that the early 
appearance and strong development of the ocelli in the larvae of both 
Limulus and the scorpion are, in view of their retention in later lifé, with 
diminished force, rather suggestive of their having been the first eyes of 
the ancestral forms. 
As the swimming legs are clearly a secondary acquirement their larger 
size and probably that of the other legs also, is a purely larval feature in 
Figure 24 Dorsal and ventral views of last larval stage of Limulus before the appearance of the 
telson. J, liver tubule; J, chelicera; op, operculum. (From Kingsley) 
line with the greater size of the lateral eyes, both of these being coeno- 
genetic larval characters developed in connection with the greater agility 
of the larva. The larvae of Limulus [see text fig. 24] possess relatively 
longer legs than the adults, and this is especially notable in the last pair 
that projects considerably beyond the carapace. A still better analogy is 
found in the lively megalops stage of the crab [see text fig. 23] where 
immense eyes and long legs are correlated features. 
