138 
THE TURBELLARIA. 
§$ 127, 128. 
CHAPTER VIII. 
ORGANS OF SECRETION. 
§ 127. 
No special organs of secretion have yet been found with the Turbellaria, 
although these animals, and especially the Dendrocoéli, secrete from their 
cutaneous surface an extraordinary quantity of mucus.” 
CHAPTER IX. 
ORGANS OF GENERATION. 
§ 128. 
The Turbellaria propagate by transverse fissuration, and by the means 
of genital organs. 
In the smaller Rhabdocoéli, which have no trace of genital. organs, the 
transverse fissuration is the rule.” 
It is, however, probable that at cer- 
tain epochs of their lives, genital organs are developed, and therefore, that 
they multiply also by eggs. 
With both the larger Rhabdocoéli, and the Dendrocoéli, the genital and 
copulatory organs of both sexes are situated upon one and the same individual, 
so that they are capable of self-impregnation ; but there is generally a re- 
ciprocal copulation.” This genital apparatus is very complex, and as the 
contents of its various parts have not yet been subjected to a careful analy- 
sis, it is not positively certain that the right interpretation of them is 
given. 
1 It is yet undecided whether the subcutaneous 
cell-like bodies of the Dendrocoéli have any relation 
to this secretion. ; 
1 Dugés (Ann. d. Sc. Nat. XV. p. 169, Pl. V. fig. 
15) has observed a voluntary transverse fissuration 
with Derostomum leucops. I have been able to 
follow the very regular fissuration of Microsto- 
mum lineare, where each unseparated half of the 
body began to halve again, and then these four pieces 
also each divided, and so finally the body appeared 
worked by seven transverse furrows, into eight 
divisions. 
I must here remark, to prevent an error, that I, 
contrary to Orsted (loc. cit. p. 73), regard these 
two mentioned species as distinct; for Derosto- 
mum leucops, Dug.,is without the reddish brown 
eye-dots and the prehensile organs, which are found 
with Microstomum lineare, Orst. The wonder- 
ful reproductive power of the sexless Planariae, 
* (§ 128, note 1.) See Leidy (loc. cit.) ; he 
found that with Phagocata (Planaria) gracilis, 
and which can be multiplied artificially by divisions 
in all directions, would lead us to infer that they 
propagate also from accidental divisions, to which 
their, vulnerable nature is constantly exposed.* 
2 Orsted (loc. cit. p. 21, Taf. IIL. fig. 53) and 
Ehrenberg (Abhandl. d. Berl. Akad. loc. cit. p. 
178, Taf. I. fig. 2, 3) affirm to have seen ovaries, 
testicles, copulatory organs, and eggs with Micro- 
stomum lineare, and many other allied Rhabdo- 
codli, such as Gyratria, Vortex, and Strongylo- 
stomum ; but the details they have given are too 
imperfect to allow definite opinions upon this or- 
ganization. I must here ask if these animals have 
not been confounded with the sexless larve which 
multiply by fissuration like those of Medusae. 
8 Coition has often been observed with Planaria 
and Mesostomum, and has been figured by Baer, 
Duges, and Focke. 
this subdivision could not be carried successfully 
beyond three or four parts. —Ep. 
