24 Gr. O. Pars. 



The Ovaria are wholly confined to the tail and the 

 genital region, and extend in the form of 2 narrow tubes 

 along the intestine as far back as to the middle of the 

 antepenultimate caudal segment. The ova contained in the 

 marsupial pouch are generally arranged in 4 longitudinal 

 rows, and are partly concealed by the richly ramified 

 glutinous gland. 



The testes form 2 rather narrow bags confined to the 

 anterior genital segment, each sending off a somewhat 

 flexuous duct, which enters the corresponding sexual ap- 

 pendage, debouching on its tip. 



As to colour, the body in both sexes is highly pellucid, 

 with only a slight greenish or yellowish tinge. The caudal 

 rami never exhibit, as in most other species, any trace of 

 pigmentation. 



Biological Observations. 



Rather a large number of specimens of this beautiful 

 form developed in my aquaria, and were watched during 

 the whole summer. They rapidly passed through their 

 larval stages, and in the course of about a fortnight reached 

 to maturity. Male and female specimens were present in 

 about the same number, the former being at once recognized 

 by their enormously developed antennæ. The swimming 

 motions of the animal are very graceful, constituting, as a 

 rule, a perfectly even dart through the water in various 

 directions, during which the belly is always turned upwards. 

 These movements are chiefly effected by the almost un- 

 interrupted, rhythmical swinging of the branchial legs, the 

 tail being used merely as a steering apparatus, twisting now 

 to one, now to the other side, according to the direction of 

 the course. The animal is, however, also enabled, by a 



