364 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the optic ganglion is well developed, and has the form of a spherical 

 mass situated laterally at the base of the antennary nerve. The optic 

 ganglion comprises a large number of ganglionic cells, but does not 

 form a solid mass. There is an irregular ramifying cavity lined by a 

 loosely compacted non-cellular structure, which represents the remains 

 of retinal rods. It appears that the ganglionic cells which originally 

 formed a cup-shaped mass round the base of the retina have grown 

 round the base of the rods and have completely enveloped them. The 

 optic nerve is well developed, and is broadly expanded within the 

 ganglion. It extends backwards through the ganglionic substance of 

 the brain, but decreases rapidly in diameter. At its actual point of 

 attachment with the white matter it is exceedingly slender. 



The skin overlying the optic ganglion is wholly undifferentiated, 

 and bears papillae precisely comparable to those of the surface in the 

 near vicinity. The epidermis is not specialized to form a cornea, the 

 lens is entirely absent, and there is no black retinal pigment. The 

 antennary nerve appears to be considerably stouter than usual. 

 Possibly, as some compensation for its blindness, the antenna? are more 

 sensitive in Typhi operipatus than in other forms. A curious scale- 

 bearing patch on the lower surface may well be sensory. The brain 

 differs rather noticeably in shape from those of the species figured by 

 Balfour and Bouvier. 



The principal characters of the genus are thus summarized. The 

 number of legs is nineteen or twenty. The inner jaw shows a diastema 

 and a saw of denticles. The legs have four complete spinous pads. 

 The nephridial openings of the fourth and fifth legs are situated on the 

 third pad. The feet have two distal papillae, one anterior and one 

 posterior. The genital opening is between the penultimate pair of legs. 

 There are receptacula seminis, with two ducts opening into the oviducts. 

 Receptacula ovarum are present. The oviducts are united for some 

 distance in front of the ovaries. The ovaries are completely fused, with 

 a single cavity. They lie closely pressed against, but not directly attached 

 to, the floor of the pericardium, to which, however, they are connected 

 posteriorly by means of a funiculus. The ovary is exogenous, i.e. it is 

 studded with follicles, in which the maturing ova lie. The ova are 

 large and heavily charged with food-yolk ; they measure about 1 ■ 5 mm. 

 in their long diameter. The embryo is without a trophic vesicle. The 

 uterine embryos are of about the same age. The unpaired part of the 

 vas deferens is of very great length. The spermatophores are long, with 

 a horny coat and cap. The skin-pigment is brown, disappearing in 

 course of time in alcohol. Well-developed coxal glands are present in 

 the legs. A single crural gland is present in the male in each of the 

 two pre-genital pairs of legs. The accessory glands of the male open 

 separately on the ventral surface between the genital opening and the 

 anus. 



The absence of eyes, and the peculiar patch of highly modified so 

 on the lower surface of each antenna, may be regarded as evidence of 

 specialization. They are not shared by any other genus of Ony- 

 chophora. The affinities of Typhi 'operipatus are primarily with its 

 nearest geographical neighbour, Eoperipatus. 



