ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
337 
reflector a tapetum, the striated body a rhabdom, tho surrounding cells 
a retin ula ; but Chun and Sars agree in regarding the organs in question 
as sui generis. Some of the results of R. Yallentin and J. T. Cunning- 
ham (1888) are confirmed, but Chun’s analysis is more complete. 
The facetted eyes. — The structure of the stalked eye of Euphausia 
corresponds closely with that described in Mysis by Grenacher. In 
some abyssal forms, the eye is very distinctly divided into a front and a 
lateral region, the former with enlarged facets. This is very well seen 
in Nematoscelis mantis , and in extreme differentiation in Stylocheiron. 
The most important deviation from the Mysis- type is in the absence of 
pigment-cells between the rhabdoms, these being replaced by pigmenta- 
tion of the retinal cells themselves. 
The cornea in Euphausia is flat, while in all other genera it has a 
convex curvature unusual in aquatic animals. It consists of at least two 
shell-like lamellae ; its formative cells lie in pairs above the crystalline 
cells, and are remarkable for their vesicular sickle-shaped nuclei. As 
in Decapods, there are four crystalline cells, but on two planes, not on 
one. Seven visual cells are grouped around each rhabdom. But it may 
be enough to state that in his description and interpretation Chun 
agrees with Grenacher and Exner, and disagrees as emphatically with 
Patten. 
Vision in the Deep-sea Schizopods. — The “ front eyes ” of Nematoscelis 
mantis and Stylocheiron are the most perfect “ darkness-eyes ” that we 
know. They see objects which are not illumined by light from the 
luminous organs of the animal itself, while the lateral part of the eye 
perceives what the luminous organ shines upon. The “ front eye ” will 
perceive shadowy outlines, the “ side eye ” is adapted to receive more 
detailed pictures. In connection with what is known as to the move- 
ment of the pigment in illumination and in darkness, it is interesting to 
find that in the abyssal forms above-mentioned, the retinal pigment has 
disappeared, and the iris pigment is constantly in the position proper to 
darkness. Even in Stylocheiron mastigophorum , which comes to the sur- 
face occasionally, no displacement of the iris-pigment could be detected. 
The absence of retinal pigment is a sure sign of abyssal life, and forms 
with “ front eyes ” are almost certainly “ day-blind.” The peculiar con- 
vexity of the cornea may act as a compensation for the lack of pigment. 
Prof. Chun’s communication is one of great interest, deserving an 
even longer summary, but in conclusion we shall only add that he 
applies his results to corroborate the otherwise probable conclusion that 
Euphausia is the more primitive type, whence have been derived in 
ascending order, Thysanoessa, Nematoscelis , and Stylocheiron. 
Early Development of Cirripedia.* — Mr. T. T. Groom, after an in- 
troductory statement as to methods, times of oviposition, and the size 
and shape of the ova, &c., gives an account of the embryonic develop- 
ment of Cirripedes, chiefly illustrated by Lepas anatifera. He next dis- 
cusses the free nauplius, and the first two larval stages, and afterwards 
proceeds to an account of their physiology. The fifth part of the 
memoir is devoted to general considerations, and the sixth to a biblio- 
graphy. 
* Phil. Trans., 185 (1894) B, pp. 119-232 (15 pis.). 
2 A 
1894 
