298 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in circnm-equatorial waters in the Atlantic, Pacific, and Indian Oceans. 

 The collection included Giinther's Branchiostomum pelwjicum and two 

 new species. All must be referred to the genus Amphioxides Gill, for 

 which the new family Amphioxididse is proposed. The diagnosis reads 

 as follows : — Pelagic Acrania without peribranchial space, with a slit-like 

 mouth lying to the left, with branchial slits on the ventral median line, 

 with the pharynx divided into a dorsal nutritive, and a ventral respiratory 

 portion. In Amphioxides pelagic us (Giinther) the notochord runs to a 

 point at the caudal end, and there are 15 post-anal myotomes; in 

 A. voddivm sp. n. the notochord ends bluntly in front of the caudal end, 

 and there are 11 post-anal myotomes ; in A. stenurus sp. n. the myotomes 

 are 55 pre-anal and 15 post-anal, and the posterior end is very much 

 narrowed. The author promises to discuss these forms in detail, and to 

 show why they cannot be regarded as neotamic larval forms. 



Eye of Bdellostoma stouti.* — B. M. Allen recalls the observations 

 of Johannes Miiller, who noted the absence of eye-muscles, the lack of 

 a crystalline lens, the homogeneous character of the eye-capsule, and 

 the total absence of pigmentation in the eye-structures. By means of 

 serial section, Allen has amplified these observations. The eye is im- 

 bedded in a mass of fat lying beneath a transparent patch of skin on 

 the side of the head ; no traces of eye-muscles are to be seen, and 

 Kupffer found none in the embryo. A slender optic nerve can be traced 

 through the mass of fat to the eye-ball. In some cases, the eye is 

 wholly imbedded, not reaching to the surface of the mass of fat ; in 

 other cases, the corneal portion is flattened against the integument. 



The size and shape of the eye-ball, the thickness of the retina, and 

 the presence or absence of a persistent choroid fissure, are subject to 

 great fluctuation. 



A section of the eye shows the sclerotic and choroid coats, together 

 with the inner layer of the cornea, to consist of a homogeneous 

 unpigmented layer of connective tissue. The optic cup remains in a 

 primitive condition. The inner layer is not directly apposed to the 

 outer, there being a distinct interval between the two. The inner layer 

 shows more or less clearly marked retinal cells ; the outer layer is 

 composed of a single layer of unpigmented cubical cells. 



Nervous System of Cyclothone acclinidens.f — August Gierse has 

 made a study of the brain and cranial nerves of this small pelagic deep- 

 water Teleostean, and finds that there are divergences in several respects 

 from the common condition of affairs in bony fishes. The skull is a 

 persistent chondrocranium ; the whole skeleton is cartilaginous ; there 

 are no scales. The brain is long and narrow ; the cerebral hemispheres 

 are inconspicuous ; the thalamencephalon is exposed ; there are two 

 independent epiphyses ; there are two symmetrical pineal nerves ; the 

 parapineal organ is a simple evagination of the ventriculus communis 

 with a terminal spindle-shaped expansion in close apposition to the pineal 

 organ ; the connection between hypophysis and infundibulum is a solid 

 nervous strand ; the mid-brain is strongly developed, but with an im- 



* Anat. Anzeig., xxvi. (1905) pp. 20S-11 (11 figs.), 

 t Morphol. Jahrb,xxxii. (1904) pp. 602-88 (3 pis.). 



