194 REPORTS ON THE STATE OF SCIENCE. 
osphradium. Some of its branches pass directly to the osphradium, 
another one joins the branchial nerve, from which nerves pass to the 
osphradial epithelium. 
The two large lateral lobes are extremely interesting. They are not 
found in other lamellibranchs. The nerves arising from them innervate 
the mantle folds. In P. jacobeus the eyes are more numerous and 
larger on the left valve, those on the right valve being small. The same 
difference exists between the two lateral lobes of the visceral ganglion in 
size. In P. maximus and P. opercularis the same difference in size of 
the two lobes corresponding to the number of eyes on the mantle folds 
exists, and in the three species examined the relative difference between 
the two sides is parallel with that of the number and size of the eyes on 
the mantle folds. From this alone it might be safely assumed that the 
lateral lobes of the visceral ganglion are due to the development of eyes 
on the mantle and are concerned with the innervation of these. This 
view was strengthened by the discovery that in several cases the nerve 
fibres passed direct from the visceral ganglion to the eyes. The eyes 
were formerly supposed innervated solely by the circumpallial nerve. 
The osphradium in Pecten, Arca, and Mactra, the species so far 
examined, is innervated by the visceral ganglion. It was in the latter 
species that Pelseneer obtained evidence of its innervation from the 
cerebral ganglia, and believed this to prevail throughout the Lamelli- 
branchiata. I believe the innervation is always from the visceral 
ganglion, though some fibres may pass from the cerebral ganglion, 
through the visceral, and into tue osphradial nerve. These, however, 
would be few in number, and in Pecten can only be seen passing into the 
branchial nerve. It is impossible to say at present whether the fibres 
passing from the branchial nerve to the osphradium contain any of 
these. 
Whilst examining the mantle edges of Pecten jacobeus I was able 
to discover the presence of a transversely striated muscle similar to that 
present in the adductor muscle of Pecten. A short paper on these has 
been published this year in the “ Anatomische Anzeiger.’ They occur 
between the eyes, and cause the rapid movements of the velum which 
take place and enable the animal to swim. 
It is often difficult to start a Pecten swimming, for ordinary stimuli 
simply cause a closure of the valves. A starfish brought before the 
valves, however, immediately causes the animal to swim. The same 
effect can be produced by the injection of starfish pulp just between the 
mantle lobes. Similar injection of sea-water or water with small par- 
ticles does not produce this effect. It is evidently not due to visual or 
tactile stimuli, and I am endeavouring at present to determine the action 
of the osphradium and abdominal sense organs in the perception of this 
stimulus. 
