THE REPRODUCTIVE SYSTEM OF E. SUPERBA 



339 



the inner or front margin of the median lobe ml, beyond the end of the lateral process 

 pi, there is always a small additional process pa; in one specimen there were two 

 additional processes." A very small spine-shaped process d on the inner lobe il has 

 been seen in one or two specimens of E. superba. 



There is nothing that I can add to this account of the adult petasma, except to say 

 that I have not found the secondary process c on the membranous expansion b of the 

 proximal process as frequently as John did. In fact, in most of the adult males examined 

 by me it was completely absent. It may be developed only when certain conditions 

 occur, or may even be a regional variation. 



Fig. i6«. Mature petasma, inner and middle lobes from behind (reproduced from John's paper). 

 X 30. a, distal expansion; b, foremost expansion; w/, middle lobe; pa, additional process; pi, lateral 

 lobe; pp, proximal process; pt, terminal process. 

 Fig. idb. Terminal and proximal processes from in front, x 30. c, spine; d, spine-shaped process. 



In my observations, two additional processes />« occur more frequently on the median 

 lobe than one, and I have also seen from time to time the small spine d on the inner 

 lobe. On p. 207 of his report, John draws attention to the fact that processes of a future 

 moult can be displaced, perhaps in fixation, and by penetrating the chitinous coat 

 give a false impression of the presence of an additional process. I have frequently 

 noticed this condition, while examining the developmental stages of the petasma. 



The modification of the second pair of pleopods (Fig. 17) proceeds rather differently, 

 and does not begin until the petasma is well established in the first pair. The tip of the 

 auxiliary lobe at exhibits a cleft on its outer side (Fig. 18) which grows rapidly and divides 



