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SIDNEY F. HARMER. 
doubted, and Salensky’s account of them is quite accurate. 
The latter observer has figured sensory hairs on the tentacles 
of an advanced bud of L. crassicauda, but has fallen into a 
singular error in denying their existence in the adult, as in 
this very species the sense hairs are undoubtedly well developed 
in the mature animal. 
According to my own observations, the nervous system has 
the following characters (PI. XIX, fig. 1). The dumb-bell 
shaped ganglion ( ga .) lies transversely across the intestine, 
immediately on its anterior or oral side (fig. 11). In sections 
of L. Tethyse (fig. 16) it is seen that the organ consists 
medianly of a fibrous commissural portion in which there are 
no ganglion cells, and of two lateral ganglia, in each of which 
the cells form a layer round the outer end of the commissure. 
In these preparations it is not possible to distinguish the 
outlines of the ganglion cells, the number of which is, how- 
ever, clearly indicated by the nuclei. There is no doubt that 
the central portion of the ganglion is really fibrous, as above 
described; and there is no trace whatever of a central duct, 
whose presence is required on the hypothesis of the generative 
nature of the organ. The ganglion can be easily observed in 
any individual of all the species I have examined, and is found 
not only in the buds but also in the adults, whether the latter 
are provided with generative organs, male or female, or are 
sexually immature : — It can be discovered in sections as 
readily as in the living animal. 
The peripheral nervous system is most easily examined in 
the living condition, L. crassicauda, on account of its great 
transparency, forming a most favorable species for investiga- 
tion. The most conspicuous part of the peripheral nervous 
system is formed by a pair of tactile prominences on the 
posterior wall of the calyx (already described by Vogt (12) and 
Salensky (15) in other species), and by the strong ganglionated 
nerves connected with these organs. From each end of the 
ganglion passes off a strong nerve which swells into an en- 
largement formed of bipolar cells (fig. 1, gas.). From the 
end of the latter a nerve passes, without branching, to the 
