INVERTEBRATA, CRYPTOGAMIA, MICROSCOPYj ETC. 61 



extremities ; basal tube corrugately jointed between the internodes ; 

 cells tubulous, hiserial, unilateral, adnate to eacb other, gradually 

 shorter outwards, apertures thickened, arranged in companies of five 

 to ten pairs on each internode, straight, and much inclined outwards. 

 Two tapering, slender, hollow processes, jointed to basal tube imme- 

 diately behind the outer cells of an internode ; not constant, some- 

 times a fresh branch taking the place of one. These setaceous 

 processes frequently have septfe across them at irregular intervals, 

 and are sometimes branched. Their length varies much, often three 

 times the length of an internode, sometimes quite short, one of a pair 

 frequently much shorter than its fellow, and sometimes club-shaped, 

 Masses are frequently found cast upon the beach without these 

 ajDpendages, as they soon drop off when dead. Ovicells not seen. 

 The animal has eight tentacles. 



The only species with which it has any affinities is Serialaria 

 Australis, described by Eev. J. E. Tenison Woods, in a paper read 

 before the Eoyal Society of N. S. W. 4th July, 1877, and, like it, has 

 peculiar characteristics, notably the fact of the cells being biserial, 

 which will necessitate a modification of Lamarck's generic description. 



Mr. Majilestone recently obtained the same species alive, and 

 found on a cursory examination that the tentacular crown seemed to 

 arise from a calyx, as in the fresh-water Polyzoa.' 



Arthropoda. 



Unicorneal Eye in Tracheata.* — An important paper on the struc- 

 ture of the simple eyes or stemmata of Myriapods and Arachnids, is 

 contributed by Prof. V. Graber, who has investigated among Myriapods, 

 Scolopendra, Julus, and Lithobius, and among Arachnids, Scorpio, 

 Buthus, Epeira, Tegenaria, and Thoraisus. 



The simple eye is formed externally by a doubly convex thickening 

 of the chitinous cuticle ; this thickening, the cornea-lens, resembles the 

 general cuticle not only in its lamellar structure, but also in the 

 presence of fine pore-canals. 



Just as the cornea-lens is formed by a thickening of the cuticle, 

 so the next layer, the so-called vitreous body, is a special development 

 of the hypoderm, with which it is perfectly continuous. It consists 

 of a single layer of transparent, double-contoured cylindrical cells, 

 separated by small intercellular spaces. The so-called iris of Buthus, 

 &c., is produced by a development of pigment in the cells of the 

 same layer which lie beneath the circumference of the cornea-lens. 



Beneath the hypoderm cells is a delicate inner cuticle or limitiug 

 membrane (liypodermale Grenzhaut) : this, on reaching the eye, splits 

 into two layers, one of which, the prceretinal lamella or so-called 

 hyaloid membrane, bounds internally tlie cells of tlie vitreous body, 

 thus having the same relation to them as the whole inner cuticle has 

 to the hypoderm. while the other layer passes directly inwards, i.e. 

 away from tlie surface of the body, and forms an investment or sclerotic 

 to the whole retina. The latter is therefore enclosed between these 

 two layers of the inner cuticle, which together form a capsule per- 

 forated only by the optic nerve. 



* ' Aivli. Mikr. Anat.; xvii. (1879) p. 58. 



