NOTES AND MEMORANDA. 
285 
other branches. This opinion seems especially defensible when we 
examine the visual organ, which may, in these species, assume very 
distinct forms, and some of which recall the eyes of the Mollusca 
or of the Vertebrata, whilst others may be compared to the optic 
point of lower animals. These considerations have naturally led me 
to investigate whether in this group of Worms some types might not 
be met with, possessing rods analogous to those of the Crustacea. 
The results which are found to justify this hypothesis are known. 
Among the Vermilia we have found eyes exactly comparable to those 
of the Lichomolgus, and reduced to two elements so similar to the rod 
of the Crustacea, that the same name cannot be withheld from them. 
Among Protula, Psygmobranchus, &c., one alone of these bodies suffices 
to constitute the organ, whilst the study of Dasyclione recalls a more 
elevated form, that of Epimeria, for example. 
Often among the Crustacea, as I have mentioned with reference to 
the Lichomolgus, &c., the rods may originate from a common pigmen- 
tiferous base. But what is such an arrangement if not the exact 
representation of that presented to us by various worms (Protula 
intestinum, Vermilia clavigera, &c.) ? The analogies go on multi- 
plying in this way as one advances in the study, and thus show in the 
strongest manner the close relationship which exists between the 
optical elements of these diverse animals. 
Such are the principal results of my researches ; these, however, 
must not be regarded as forming a complete history of the optic rod, 
to the study of which I have only attempted to bring some new facts. 
I hope soon to be able to complete them by a new series of observa- 
tions and experiments instituted with the view to the study of the 
development of the rod, and to determine what characters and what 
relations it may present in the different ocular forms.” 
The Minute Structure of Stromatopora and its Allies. — Professor 
H. Alleyne Nicholson and Dr. J. Murie have made a lengthy com- 
munication to the Linnean Society on the above subject. Stroma- 
topora they point out, even at the present moment, occupies a 
most unsettled and uncertain position, while hints and doubts flow 
freely as to whether it be allied to the Calcareous or the Siliceous 
Sponges, to the Foraminifera, to the Corals, to the Hydrozoa, or to 
the Polyzoa, or whether it may not be a heterogeneous assemblage 
of dissimilar forms, or perhaps the representative of a special and now 
extinct group of organisms. Unfortunately, the animal itself cannot 
be appealed to as affording evidence towards the solution of this 
problem, the remains of its habitation, or its skeletal structures alone 
offering data upon which any judgment on this disputed point may be 
arrived at. Their object is to present the results of a careful exami- 
nation of a large number of specimens and sections of different forms 
of Stromatopora and of related groups. These results, it is hoped, 
will serve to throw some light upon the anatomy and systematic 
position of Stromatoporoids, though, as a matter of course, some 
points have necessarily been left doubtful or unsettled to a large 
extent, owing to the impossibility of obtaining access to many of the 
original specimens described by earlier observers. 
