260 Dr. E. Bergli on the 



controversy as to the systematic position of these animals has 

 broken out. H. von Ihering, as is well known, has adopted 

 a former notion of Milne-Edwards (1857), and has endea- 

 voured to demonstrate that the so-called lung of the Onchidia 

 in its principal mass morphologically represents the dilated 

 terminal section of the kidney of other marine Ichnopoda, or 

 a cloaca. According to Ihering, therefore, the Onchidia 

 would be the lowest forms, the stem-forms, of his so-called 

 "IS'ephropneusta" (stylommatophorousPulmonata), and should 

 perhaps be incorporated with the order Pulmonata ; but they 

 come near to the marine naked ]\[ollusca *, and from these 

 (especially perhaps the Phanerobranchia) the Onchidia 

 should be derived. 



There is, however, much to be urged against this theory of 

 Ihering's, as has, indeed, already partly been done by Semperf. 

 Semper's objections are directed principally against Ihering's 

 derivation ot the lung of the " Nephropneusta " from a terminal 

 section of the kidney of the Phanerobranchia, and he demon- 

 strates that the walls of the pulmonary cavity of the Onchidia 

 contain no lu'inary concretions, and consequently cannot 

 belong to the kidney, which, on the contrary, is enclosed by 

 the lung. This kidney also consists of the two typical sec- 

 tions, the true kidney with the urine-chamber and the urinary 

 duct ; close by there is a ]ndn)onary cavity, which, conse- 

 quently, cannot represent the terminal section of the kidney. 

 The lung, according to Semjjcr, has not originated from the 

 kidney of the Phanerobranchia, but is (as in the other 

 Stykimmatojihorn) a branchial cavity adapted for aerial 

 res])iraTion, which has been develojjed from tlie branchial lung 

 of the Basomrnatophora. In the characters of the generative 

 organs of tlie Onchidia^ moreover, he finds a confirmation of 

 his conception of the afhiiities of these aninuds, which he 

 regards as Pulmonata. 



To the derivation of naked Pulmonata (such as the On- 

 cJiidia) from sliell-bearing forms there is, on the whole, 

 nothing to be objected, especially within this group. So 

 many transitional forms occur here, from animals with a 

 large external shell which can contain the whole animal, to 

 those with a rudimentary shell which cannot conceal the 

 animal {Testacella) , and, further, to those with the shell 



* H. von Ihering, ' tlelDer die systeniatiscLe Stellung von Peronia,^ 

 1877, p. SO. See also ' Anatomie des Nervensystenis imd Ph ylcgenie der 

 Molhisken," 1877, p. 223 : — " We might perha] s with equal justice refer 

 them to the Phanerobranchia as to the Nephropneusta." 



t Semper, " Einige Pemerkungen liber die Nephropneusten, v. Ihering," 

 in Arb. zoolog. zoot. Institutin Wiirzburg, iii. 1877, pp. 4fe0-488. 



