MORPHOLOGY OF MBLIBE 565 



it is evident that this type is derived from the third type 

 of Lang. 



The hermaphrodite gland lies in the caudo-ventral region of 

 the perivisceral cavity and consists of a great number of 

 bilobed acini (PI. 37, fig. 81, Ot). The eggs and the spermatozoa 

 are situated in different regions of the same acinus, which is 

 easily demonstrable in the neutral phase, that is when the 

 male or female germ-cells are in a regressive or progressive 

 stage of growth ; as soon as the one has gained the ascendency 

 either a male or a female phase appears which seems to take 

 over the entire acinus. At such a time the small duct system 

 which leads from the indifferent or resting region of the acinus 

 is nearly crowded out by the actively employed ducts, and then 

 the acinus may give the appearance as having only a single 

 duct arising from it. That is, during the ripe male phase, the 

 female germ-area with the ducts of any acinus may be crowded 

 to the periphery or to one side in such a way so as to give the 

 appearance of only one duct system leading out from that 

 acinus. However, in any stage of either male or female phases, 

 the two duct systems may be discerned in some of the acini. 

 I cannot determine with any certainty whether this species is 

 protandrous or not, as I have not studied sufficiently young 

 individuals on this point. All the individuals, whose glands 

 I have sectioned, have shown ripe spermatozoa in the acini 

 and also ova. 



Pelseneer (1895 : 31) states that protandry ought to be 

 regarded as a general phenomenon in Euthy neurons 

 gasteropods. That this is notoriously the case in pul- 

 monates, and that it has been recognized in various opistho- 

 branchs which have been studied from this point of view, viz. 

 Lohiga,,the Thecosomatous pteropods, e.g. C Ho- 

 st riola, &c. ; nudibranchs, among which he observed it in 

 A e 1 i d i a and E 1 y s i a ; and lastly C 1 i o n e 1 i m a c i n a 

 (Gymnosomata), in which he noticed that individuals of 

 a length of 15 mm. (or less) do not as yet show any ova in their 

 genital glands, but stages in the development of spermatozoa 

 only. He also found that the ovogenous and spermatogenous 



