31 
1907-8.] Notes on some Turbellaria from Scottish Lochs. 
those of Hydra not only in their smaller size but in the possession of four 
instead of three barbs. 
In the skin of Microstoma from the shores of the Scottish lochs in 
places where Hydra is abundant, I have found the three forms of nemato- 
cyst which are characteristic of Hydra. In some blind Microstoma from 
deep water where Hydra was absent there was no nematocyst. 
This blind form without nematocysts was first described by Du Plessis 
in 1897 ; and later, Zacharias raised it to specific dignity under the name of 
Microstoma inermis. I do not believe that this species is a good one, for 
two reasons. 
In the first place, in nearly all Turbellaria which inhabit both deep 
and shallow water one finds this degeneration of the eyes (e.g. Automolos 
Morgiensis) in the deep-water forms. 
In the second place, the nematocysts of the Microstoma in littoral waters 
are derived from the Hydra on which it feeds, in much the same way 
in which Grosvenor found that the iEolids derive their nematocysts from 
their coelenterate prey. 
In transverse sections through a Microstoma which has recently fed 
upon Hydra, nematocysts are found in three places : — 
(1) In the gut. 
(2) Surrounded by mesenchyme cells in the space between the gut 
and the ectoderm. 
(3) Under the ectoderm. 
I hope to show in a further paper the mechanism by which this trans- 
ference is accomplished ; and further, that all true nematocysts with a 
thread capable of expulsion, found in Bhabdocoels, are obtained in a 
similar manner. 
Gonads. 
During the greater part of the summer Microstoma reproduces entirely 
by budding, and it is only in September that I have first found sexual 
forms on Loch Tay and Loch Lomond. 
In both years male forms were common long before I could find any 
females. But in two cases, in sections of fully developed male indi- 
viduals, I found the testes degenerating, and bodies which looked very 
like ova in the mid-ventral line. I hope to be able to get more material 
this year, and finally decide how far Microstoma can be described as 
protandrous. 
