28 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
pigmented part of the eye, and the eye would necessarily be regarded 
as inverted. It need only be said that there is no evidence in my prep- 
arations that nerve fibres and retinal cells are thus related, though 
that is clearly the condition which Claus (91), Hartog (’88) and 
Richard (91) had in mind. ‘Therefore, if the relation between, the 
cells of the eye and the axis cylinders that arise from them is to be re- 
garded as evidence that the eye is inverted or not,— that is, that the 
recipient portions of the nerve fibre are or are not directed toward the 
pigment and away from the exterior,— we must, at least in this case, 
look upon such evidence as distinctly against the view that the median 
eye in Copepoda is inverted. 
h. The Neurofibrillae— But more direct evidence than that 
hitherto presented is at hand relative to the character of the eye in 
Eucalanus; it is based upon the relations existing between the end- 
fibrillae of the nerves and the retinal cells. The character of the nerve 
ending in the visual cells of Eucalanus has been investigated by Hesse 
(:01, p. 349) in the course of his studies on the eyes of invertebrates. 
He states that he was led to this investigation by a desire to know 
whether or not the relationship believed to exist between the median 
eyes of Crustacea and the eyes of flatworms, did not also extend to 
the “‘lichtrecipierenden Theile der Sehzellen.” He had previously 
shown (Hesse, ’97) that in Planaria and its allies there is in the visual 
cells a “Stiftchensaum....dessen einzelne Stiftchen nichts Anderes 
sind als verdickte und vielleicht stofflich etwas verinderte Enden von 
Neurofibrillen, welche von der Nervenfaser in die Sehzellen einstrah- 
len” (Hesse :01, p. 350). With regard to the Copepoda he says (:01, 
p. 350): “Die Untersuchung hatte das vermuthete Ergebnis: ich fand, 
dass das ‘Stabchen’ bei diesen Formen ein Stiftchensaum ist.” 
His preparations of Eucalanus elongatus showed this condition the 
most clearly, although the conditions in Eucalanus attenuatus and in 
Calanus gracilis were practically the same. 
I have been unable to confirm, by my preparations, Hesse’s state- 
ments with regard to the presence of a Stiftchensaum in Eucalanus 
elongatus. ‘The iron-haematoxylin method following corrosive-acetic 
fixation (which Hesse seems to have employed) is the least successful 
of any that I have used in showing even the general relations between 
axis cylinders and retinal cells. 
But any preparation will show in the basal region of the retinal cells 
an almost indistinguishable striation of the cytoplasm. ‘This striated 
appearance is seen to best advantage in vom Rath preparations (Plate 
1, Figs. 5, 7, 9), though it is shown to some extent in sections stained 
