832 The American Naturalist. [September, 
brought out emphasize the similarities which exist between the Sipun- 
culids and Phoronis. He also thinks that in spite of the absence of 
metamerism there is nothing in the anatomy of the adult which could 
not be explained on the theory of lost segmentation in these worms, 
while he institutes a striking comparison between the gonads of the 
Polychete placed on the posterior side of a dissepiment and those of 
Sipunculus attached to the posterior surface of the pharyngeal retractors. 
Sipunculus nudus.—H. B. Ward describes? the anatomy and 
histology of this Mediterranean form. The material at command 
embraced only the anterior portions of the body, so no study was 
made of many features worked out by Andrews. ‘The histology of the 
body-wall and of the nervous system receive most attention. Among 
the many points brought out, the most interesting is the existence of a 
‘“ cerebral organ,” consisting of a canaleopening to the exterior in the 
dorsal median line, and connecting posteriorly with an area in close 
connection with the brain, which the author is inclined to regard as 
sensory, and to homologize with similarly situated organs in Phymo- 
soma and Sipunculus gouldii. The general accounts of structure given 
by Andrews and Ward agree well in broader features, but differ con- 
siderably in detail. From the evidence afforded by the nervous sys- 
tem Ward is inclined to the view that there is only a remote relation- 
ship between Sipunculus and the Annelids. 
The Eye in Blind Crayfishes.—G. H. Parker has studied è the 
eyes in Cambarus setosus and C. pellucidus. In both species the optic 
ganglion and optic nerve are present, "e latter SETI in 58 hypo- 
dermis. In C. setosus the retina has almost completel ted, while 
in C. pellucidus it is represented, bya thicker portion of “the hypodermis 
with scattered multinuclear granulated bodies. These Parker regards as 
degenerated clusters of cone cells. Thus Cambarus setosus from the 
caves of Missouri has gone farther in the line of ophthalmic degenera- 
tion than its ally from the caves of Kentucky and Indiana. 

“The Compound Eye of Crustaceans ” is the title of a larger 
paper * by the same author. He gathers together all that is known, 
adding much himself in the endeavor to solve certain problems sur- 
rounding these organs. The retina of the compound eye is composed 
of anumber of similar units or ommatidia, but the structure of the 
ommatidium varies considerably in different groups. One question 
2 Bull. Mus. Comp. Zool., XXI., No. 3, 1891. 
3 Ib., XX., No. 5, 1890. 
í Ib., XXI., No. 2, 1891. 

