THE CYCLOPEAN EYE. 37 



The larvae have now passed into what is known as the Alima 

 stage. The paired compound eyes now become stalked, and the 

 unpaired simple eye more easily distinguishable as a tiny X shaped 

 black speck, set at the base of the rostrum and between the bases of 

 the stalked eyes. As a point of interest, it may be noted that a 

 connection has been suggested between it and the pineal eye of 

 vertebrates. 



In PL vi, Fig. 5, a later alima stage is figured just prior indeed 

 to the assumption of adult form. Here the three suppressed maxil- 

 lipeds are reappearing, but extremely short (Fig. 56). In it also, the 

 three biramous walking limbs of the adult are beginning growth 

 tiny buds on the underside of the three hinder thoracic segments 

 (Fig. 5c), which until the present have from the time of hatching 

 been free from any sign or trace of appendage. 



During all these larval stages, the tiny animal leads a pelagic 

 free-swimming life, and is occasionally taken in the tow-net in the 

 sunny waters of the Channel Isles. Like other pelagic animals it is 

 glassy and colourless and a powerful swimmer. 



EXPLANATION OF FIGS. 3 5, PLATE VI. 



Metamorphoses of Squilla. 



Fig. 3. The recently hatched animal in the Erichthus or Glass- 

 shrimp stage ; actual size 4 mm. (inclusive of rostrum). 



Fig. 4. Early Alima stage of another species, ventral view ; actual 

 size 4J mm. 



Fig. 5. Advanced Alima stage, dorsal view ; actual size 11 mm. 

 (In this figure, the rudimentary three hinder pairs of 

 maxillipeds 56 ; the bud-like ambulatory limbs 5c ; 

 and the well-developed ambulatory limbs 5d, are not 

 figured for clearness sake). 



5, a mandible ; 56, one of the three hinder and rudimentary 

 maxillipeds, X 55 ; 5c, Section through the hinder part 

 of the thorax, showing the first appearance of the am- 

 bulatory limbs as buds, X 18 ; 5d, a swimmeret, X 13. 

 Lettering the same in all figures, viz : I. anterior antenna? ; 



II. posterior antennae ; III. mandibles ; IV & V. 1st and 2nd maxilla? ; 



VI, VII, VIII,, IX & X. maxillipeds; XIV XVIII. swimmerets ; 



e. paired compound eyes ; e. unpaired simple eye ; lab. labium ; 



II. branchial plate of maxilliped ; cp. carapace ; r. rostrum ; al. ali- 

 mentary canal ; a. anus. 



NOTE. Probably the two Alima forms figured, belong to the 



same species of Squilla, viz., S. desmarestii. 



