ON PTYOHODERA FLAVA. 175 



are surrounded by a mass of small refringent globules. As the 

 ova in the iudividual from which the preparation represented 

 by fig. 5 was taken appeared to be sub-mature, it seems not 

 impossible that these globules are of the nature of mucous 

 granules. Spengel says that in P. mi nut a, when the forma- 

 tion of sexual cells commences the fat-like substance begins to 

 disappear, and is finally quite replaced by ova and spermatozoa. 

 The conditions in P. flava appear to differ from this. 



The ova (fig. 6), when obtained free by artificial rupture of 

 the gonads, are seen to be surrounded at an interval by a hyaline 

 double-contoured membrane, the follicular membrane. They 

 are opaque, being filled with fine yolk granules. They measure, 

 apart from the membrane, '006 mm. in diameter. 



With regard to the shape of the gonads in the branchial and 

 post-branchial regions of the genital pleura, there is no difference 

 whatever in P. flava (cf. fig. 4a). But in P. minuta and 

 P. Sarniensis, Spengel states (loc. cit., p. 653) that in the 

 branchial region the gonads are almost always simple un- 

 branched sacs, while in the post-branchial region their form 

 becomes more complicated. 



In one instance of a male individual of P. flava I observed 

 a much elongated gonad, as long as four or five of those on 

 either side of it taken together. 



Systematic Position of P. flava, Eschscholtz (char. 



emend, mihi). 



As might be expected, the short description given by Esch- 

 scholtz, beyond indicating by the presence of the genital pleura 

 that his species belonged to the genus Ptychodera in Spengel's 

 system, fell far short of being a satisfactory specific diagnosis. 



In consequence of this, Spengel has wrongly placed this 

 species in his genus or sub-genus Tauroglossus. He does not, 

 however, finally assume this, but puts a mark of interrogation 

 against it. 



Spengel has, as it seems with justice, subdivided the genus 

 Ptychodera, suggesting the formation of the family Ptycho- 

 deridse, with the three genera, Ptychodera, Tauroglossus, and 



