
834 The American Naturalist. [September, 
by pigment cells. The transparent cells are the forerunners of the cone 
cells, while the pigment cells represent an as yet undifferentiated 
_retinular region. This view is clearly opposed to that of Watasi, 
already noticed in our pages, by which each ommatidium is regarded 
as an involution of ectodermal cells, the members of which may still 
retain their power of secreting cuticular structures. The ommatidium, 
on the contrary, is a differentiated cluster of cells in a continuous 
unfolded epithelium. Patten’s view that the ommatidium is a hair- 
bearing sense-bud receives no confirmation in Parker’s studies. 
Eyes in Arcturus.—Beddard describes the eyes in deep and 
‘shallow-water species of Arcturus. He finds that some at least of the 
deep-sea forms show evidences of degeneration in the visual apparatus. 
Thus in three species he finds the conical lens showing signs of becom- 
ing opaque, while in three others there is alteration of size and curva- 
ture. In several others the rhabdom affords similar evidence, while in 
many deep-sea forms the decrease in amount of pigment is also regarded 
as an indication of degeneracy. 
The Northern Limits of the Scorpions.— During a recent 
collecting trip to the Bad Lands of the Hot Creek Valley, in the ; 
extreme northwestern corner of Nebraska, Mr. F. C. Kenyon, a mem- 
ber of the party, found a living scorpion (Buthus sp.). This is, so 
far as I am aware, some three hundred miles further north than any 
member of the group has ever been found east of the Rocky Moun- 
tains. West of the mountains, I am informed by Mr. Henshaw, they 
extend north to Oregon and Washington.—J. S. KINGSLEY. 
Glands in Orthoptera.—H. Garman describes, in the current 
volume of Psyche, peculiar glandular structures borne between the 
ninth and tenth terga of the abdomen of the cave cricket. Their 
function is unknown ; but the author points out the- fact that scent 
glands occur in the females of certain Bombycids. Apparently he is 
not familiar with the recent literature of abdominal glands in the 
_ Hexapoda. 
Notes on Tunicates.—Herdman thinks® that the usual divisions 
of the Tunicates, while convenient, do not express the true relation- 
ships of these forms. According to him, the Synascidiz are in reality a 
_polyphyletic group, the members of which touch the Ascidiz simplices 
at various points. Hence a strictly phylogenetic classification will 
5 Proc. Zool. Socy. London, 1890, p. 365, pl. XX XI. 
6 Nature, June 11th, 1891. 5 


