470 Geoffrey Smith 



maxillae and the presence of the two i)airs of valve-like maxillipeds 

 (fig-. 4), and fiually in the complete segmentation of the thorax, differs 

 very greatly from the tnmid Praniza larva, and yet the change from 

 the one to the othev occurs in a single eedysis. In a Praniza which 

 is abüut to undergo metamorphosis into the adult male, it is always 

 to be ol)served that the neck, instead of being narrow and incon- 

 spiciious as in the young Praniza or in one about to change into a 

 feraale (fig. 5), is much swollen so that there appears to be an extra 

 Segment added to the thorax (fig. 6). This swollen region, which 

 corresponds to tlie segments of the two pairs of maxillipeds is in 

 fact the Chief formative region for the Square head of the adult male. 

 On cxaminiug such a Praniza from the ventral surface the formation 

 of the new valve-like appendages can be observed (fig. 7). Within 

 the case of the larvai first maxilliped the definitive appendage can 

 be seen with its hairs folded back upon itself and its base greatly 

 enlarged. The very peculiar valve-like structures which fold externally 

 over the orai region of the adult male can be seen developing in the 

 greatly enlarged basai joints of the larvai second maxillipeds. They 

 widen gradually to form the adult structures. It is thus seen that 

 the adult maxillipeds of the male are both formed by an enlarge- 

 ment of the basai joints of the larvai appendages, which occurs in 

 correlation with the backward shifting of the formative region of 

 the head. 



The formation of the large mandibles of the male has been 

 described by Doiirn (2) who rightly points out that they are not 

 formed within the case of the larvai manclibles. He concludes there- 

 fore that they are not homologous with the larvai mandibles, but it 

 may be suggested that an exaggeration of the process just described 

 in the case of the maxillii)eds, i. e. an enlargement of the base of 

 an appendage at the expense of its distai joints, would naturally 

 lead to the eondition actually found in the case of the mandibles. 



With regard to the rest of the body the segmentatiou of the 

 thorax conii)letely reappears; the coloured areolation of the front 

 region of the thorax is not completely formed until two days or so 

 after the metamorphosis has taken place. A word must be said with 

 regard to the liver: this in the young Praniza of botli sexes consists 

 of two lobes in the anterior thoracic region ^fig. 1 L). In the female 

 these lobes do not increase in size, but in the male during the period 

 before the final eedysis, the liver lobes grow downwards and absorb 

 the nutriment from the inflated cut. In the adult thev turn blackish 



