72 Miscellaneous. 
We may therefore conclude that the unpaired eye in all the 
Crustucea that possess it is composed of three simple eyes, placed 
anterior to the brain, with reversed optical bacilli, receiving conduc- 
tive fibres of the optic nerve upon ther outer margin, and brought so 
close together that their pigmented or choroid layers are combined 
into a single mass. 
We may detect a nearly identical structure of the visual organ in 
two other groups :— 
1. The Chetognatha, according to M. Hertwig, have absolutely 
the triple eye of the Crustacea; but, instead of being median and 
unpaired, it is repeated on the two sides of the head. 
2. Certain Planarians, Dendrocelum lactewm for example, have 
two paired eyes, which, according to Justus Carriére, have the 
structure which I adopt for one of the simple eyes united in the 
median eye of the Crustacea. 
It is probable that the eye of the Chetognatha and Crustacea is 
to be referred back to the type of the Planarians, but that the two 
former groups have no direct relationship between them. 
The method of thin sections has revealed to me some other in- 
teresting peculiarities, which I hope soon to publish in a more 
extended memoir upon Cyclops. 
The eye which most nearly approaches that of the Crustacea and 
Cheetognatha seems to be that of the Planariw. M. Justus Carriére 
has just published (Arch. fir mikr. Anat. xx. p. 160) a memoir on 
the eyes of these very primitive animals; and, according to his text 
and figures, it must be assumed that each eye of the Planaria or 
Dendrocelum represents one of the components of the eye of the 
Crustacea. It is therefore more rational to refer back the eyes of 
the Crustacea and Cheetognatha to such a primitive ancestral group 
as the Turbellaria than to seek direct approximations between the 
two former groups.—Comptes Rendus, May 22, 1882, p. 14380. 
Sponges from the Neighbourhood of Boston, US. 
Mr. E. Potts exhibited some fragments of freshwater sponges 
collected in the Cochituate Aqueduct and sent to him by the Super- 
intendent of the Boston Waterworks. Alluding to the deleterious 
effects recently attributed to this sponge, as the cause of the pollu- 
tion of the Boston water-supply, he said he was not prepared either 
to affirm or deny it. While he was well aware that a decaying 
freshwater sponge was one of the foulest things in nature, in his 
own experience he had never met with it in sufficient quantities, 
locally, to suppose it capable of tainting, in its decay, millions of 
gallons of water, as now represented. 
An examination of the sponge as to its specific relations revealed 
some peculiar facts. Primarily it was evident that the sponge was 
much “mixed,” the presence of two or more species being very 
apparent. 
One of these, with long branching finger-like processes, smooth 
