724 SUMMARY OF CURRENT RESEARCHES RELATING TO 



favour, would be contradicted by the fact that tbe enclosed balls o"r 

 globes are all constructed excentrically, whereas all terrestrial 

 crystallites are formed concentrically." 



Mollusc a. 

 American Cephalopoda.* — Professor A. E. Verrill, in addition to 

 a list of the species collected during the season of 1880, describes 

 some new forms. The genus Mastigoteuthis is the representative of a 

 new family, Mastigoteuthidce, in which the eyelids are simple, the pen 

 narrow anteriorly and having a long tubular cone connected with its 

 much wider posterior end ; the arms are very unequal, the ventral much 

 the longest ; the suckers are small and in two regular rows ; the tenta- 

 cular arms have no distinct club. The species is called M. Agassizii. 

 Eledone verrucosa is a new species, the characters of which " illustrate 

 well the uselessness of the attempts to divide the species of Octopus 

 and allied genera into groups or sections according to the relative 

 lengths of the arms ; for in this and many other cases the proportions 

 of the arms of the right side would throw it into one section, those of 

 the left side into another. The male would have to be put in a third 

 section." The writer gives also a notice of his lately formed genera : 

 Cheloteuthis (G. rapax), Calliteuthis ((7. reversa), and Alloposus (A. 

 mollis) ; the last of these is distinguished by the permanent attach- 

 ment of the mantle to the siphon. 



Simple Eyes of some MoUusca.t — Dr. P. Fraisse here describes 

 the eyes of Patella, Haliotis, and Fissurella. In dealing with the first 

 of these, he states that there is no ommatophor, that the eye itself is 

 a small vesicle 0*12 mm. in diameter, and that the epithelial cells pass 

 directly into those of the retina. These epithelial cells differ from 

 those of the tentacle by being somewhat shorter and in being more 

 closely packed ; the retinal cells are longest at the base of the eye. 

 Pigment is found most largely in the cells which are opposite to the 

 pupil. It is clear that the whole of the cellular layer which forms 

 the eye is formed of a single layer of delicate cells, the upper part of 

 which is occupied by black pigment. There is no true optic nerve, 

 nor is there any lens or vitreous body, or any real indications of these. 

 Knowing these facts, we cannot be astonished at learning that in one 

 and the same animal one eye may be, for it, well developed, while the 

 other is much smaller and much less deeply pigmented. So far as the 

 author has been able to make out he finds that the eyes of Molluscs 

 commence to be formed by an invagination of the epidermis, which is 

 at first open to the exterior ; as it becomes shut off, the retinal cells 

 become developed out of the epidermal cells, but the eye of Patella 

 remains at an embryonic stage, as compared with most of the 

 Mollusca. 



In Haliotis the eyes are large, and are placed on retractile omma- 

 tophors, and as in Patella, there is an open cup. The cavity is 

 largely occupied by a vitreous body. The cylindrical cells of the 

 epidermis pass directly into the elongated cells, and the pigment is 



* Bull. Mus. Comp. Zool., viii. x;i881) pp. 99-116 (8 pis.), 

 t Zeitschr. f. wise. Zool , xxxv. (1881) pp, 461-78 (2 pis.). 



