304 NOTES AND MEMOKANDA, 



beset by flukes, from half-a-dozon to several dozen, and a bcll-sbaped 

 tricbodina crowds tbe brancLial cavity.* 



Hermaphroditism in, and the Spermatophores of the Nephro- 

 pneustous Gasteropoda. — Dr. Pfeffer describes f tbe arrangement of tbe 

 generative organs of some of tbe Nanidina in tbe Berlin Museum ; tbe 

 genus Trochanina is founded on external characters, but tbe examination 

 of tbe internal parts has brought to light variations in structure, which 

 should lead to tbe breaking up of the genus. The forms which com- 

 pose it are distinguished by having an accessory gland to the penis 

 and by tbe absence of tbe retractor muscle of this organ ; in T. 

 Schmelziana and T. radians the seminal duct is connected with the 

 lower portion of the penis by well-developed connective tissue, but in 

 the other species it is connected by a muscle with tbe uppermost parts 

 of tbe uterus. In some still more divergent forms there is a duct con- 

 necting tbe prostate with the stalk of tbe vesicle. 



The arrangements in T. ibuensis are such as to make copulation 

 impossible, as the penis has no efferent duct, and the sole orifice is 

 that which belongs to tbe oviduct ; the presence, however, of tbe just- 

 mentioned duct atones for this structural defect, or, in other words, 

 renders the penis unnecessary. In T. percarinata the duct was like- 

 wise present, and no orifice could be detected in the penial papilla. 

 In tbe other forms there are no apparent arrangements for self- 

 impregnation, though there are difficulties, such as for example tbe 

 absence of a retractor penis, set in tbe way of reproduction by 

 copulation. 



Tbe spermatophores were found in tbe penis, or in tbe bladder, 

 and there might be, in different species, one, two, or even tbree of 

 these bodies, with fragments of others. They exbibit in most cases 

 tbe same general cbaracters ; they form a sausage-sbai^ed body in- 

 vested in a thin, white, horny covering, provided at one end with 

 a spine-sbaped projection, and continued at the other into a thinner, 

 long, dark brown tube ; this tube becomes semicircular towards its 

 free end and terminates in an enlargement, which is provided with 

 one or two crowns of spines. When acted upon by water, the contents 

 swell towards this end ; they are then seen to contain a number of 

 hyaline chitinous fibres, and some oval or lancet-sbaj^ed calcareous cor- 

 puscles, such as are generally, if not always, found in tbe penis of the 

 Zonitidce. Tbe spermatophores are, it is concluded, developed in tbe 

 flagellum of tbe penis, or tlirougb tbe whole extent of this organ ; and, 

 from tbe complexity of their structure, it is thought to be unlikely 

 that there is a second formation of spermatophores during tbe same 

 copulation period. 



Mucous Threads of Limax. — Dr. Eimer, having described | the 

 habits of Limax agrestis, and having observed that he was unable to 

 find any reference to their powers of producing mucous tbreads, 

 induced Professor Martens to make some remarks on tbe subject, § of 

 which it may be interesting to give a short account. 



* 'Nature,' xix. (1879)470. 



t ' Arcli. fiir NaturKescliiclite,' xliv. (1878) 420. 



X 'Zool. Anzoiger,' i. (1878) 123. § Ibid. 249. 



