124 Dr A. Krohn on the genus Dolioluni and its species. 



in swarms in March and April, have a red-spotted body, and the 

 alimentary canal blue or pale red. 



Fully grown individuals reach the dimensions of 1^ line in 

 length. 



B. Species with nine muscular bands, and with the gemmarium 

 upon the dorsal surface. 



1. Doliolum Nordmanni (Krohn). 



In form this species appears at first so nearly to approach 

 D. denticulatum, that they may be readily confounded together. 

 It is only upon more close examination that the characteristic 

 differences in the branchial membrane and the number of the 

 bands become obvious. The branchial membrane in this species 

 forms a flat septum stretched obliquely from above and behind, 

 downwards and forwards across the cavity of the body, with only 

 four pair of clefts. The mouth is exactly in the centre of the 

 branchial membrane. The alimentary canal in all respects re- 

 sembles that of D. Millleri. 



I have nothing to say about the generative organs and the 

 sexual relations, since all the individuals observed were asexual. 

 With respect to the gemmarium I must observe, that a peculiar 

 filiform, transversely annulated, or rather wrinkled appendage is 

 attached to its free extremity, which is found in no other species. 

 The modification of the arrangement of the muscular bands, 

 which has been already referred to, affects here the ante-penul- 

 timate band, which, in consequence of the position of the gem- 

 marium, is open above. 



This is the smallest of the species, since in its full-grown state 

 it is not more than 1 line in length. i 



2. Doliolum Troschelii (Krohn). 



I have but rarely observed this species. It is much larger 

 than that just described, as I have met with individuals more 

 than 3 lines in length. Upon the whole it resembles D. denti- 

 culatum and Nordmanni, only that the body is more elongated. 

 It is especially remarkable from its singularly broad muscular 

 bands*. The alimentary canal is quite similar to that of the 

 preceding species ; but of the branchial membrane I can say 

 nothing, since it was accidentally absent in all the specimens, 

 having been probably injured and torn off in some manner. 



* Upon superficial examination, this species, on account of its broad 

 muscular bands, might readily be taken for a very young proles solitaria of 

 Salpa punctata (Forskahl). Among the Saipts observed by me at Messina 

 (Annales des Sciences Nat. 1846), this solitary Salpa-form is the only one 

 all whose muscular bands form complete and relatively very broad circles. 



