124 MICROSCOPICAL STUDIES. 



a consequence, the radiating nerves are wonderfully numerous and 

 strong. Anteriorly they branch off to the eyes and head appendages, 

 while posteriorly two great trunks are given off to supply the swimming 

 feet and the remainder of the thorax and abdomen. The way these 

 nerves divide into a network of twigs serving the dermal glands has 

 already been noticed. 



Of Sensory Organs, the chief are the eyes, of which there are 

 three two complex lateral eyes lying on either side of a small and 

 simple median eye. The structure of a lateral eye consists essentially 

 of a very large globular corneal lens (cl.) lying in front of the true crys- 

 talline lens or " cone," behind which again is a large pigment body 

 resting upon the ganglionic mass. The corneal lens is derived from the 

 cuticle ; in some species, as in S. Edwardsii, it rests directly on the 

 crystalline lens ; in others, as in S. Gcgenbauri, and especially in S. 

 Clausi and S. Darwinii, quite a considerable distance separates the two 

 (Fig. VI.). 



The sensory setae of the peripheral nerve cells have already been 

 referred to ; the only other sensory organ is the frontal sensory organ 

 of unknown use, seen between the corneal lenses (x). It is noteworthy 

 that the Nauplius larvae of the higher Crustacea also show similar 

 organs, from which we may infer that this is an organ present in the 

 ancestral Crustacean stem. 



No heart or blood-vascular system is present. The blood or 

 coelomic fluid moves freely in the whole of the coelome or body cavity. 



Lining every part of the body wall is a peculiar stellately-branched 

 and very delicate form of tissue, called the Fat-body, wherein are 

 formed oil spheres of wonderfully large size. In some species they are 

 specially numerous, as, for example, in S. Clausi and S. Edwardsii, and 

 are symmetrically disposed. The fat-body as a whole serves as a 

 reserve of nourishment, and is especially useful when the animal 

 moults and when the reproductive function makes special drain upon 

 the vitality of the individual. 



EEPRODUCTION. In the males here figured, note the two-lobed 

 testis (Fig. VI., .), stretching across the body close to the stomach. 

 On either side is given off a long tubular vas deferens, glandular at its 

 further end and then expanding into a wider region, the spermatophore 

 pouch, wherein numerous spermatozoa lie encased in an envelope or 

 spermatophore until such time as copulation shall take place, when 

 the spermatophore being fixed by the male upon the genital segment of 

 the female, the spermatozoa break through their envelope and pass 

 individually into the oviducal openings. 



The young pass through well-marked Nauplius stages. 



