[FRASER] ON THE DEVELOPMENT OF ÆQUOREA FORSKALEA 99 
provided with a lithocyst at each side of the base. The eight lobes 
of the lips are each divided into four parts by slight indentations. 
By the time the diameter of 12 mm. is reached, the first eight 
radial canals of the fifth series, viz., those adjacent to the perradials, 
are complete and some of the next eight, viz., those adjacent to the 
interradials, have made a beginning. Tentacles have appeared on 
the bulbs of the fourth series adjacent to the perradials and the bulbs 
adjacent to the interradials are of large size. The bulbs of the fifth 
series have started to develop. The pairs of lithocysts for all of the 
bulbs of the fourth series are present. The mouth has changed very 
little. 
At 16 mm. the second eight canals of the fifth series, viz., those 
adjacent to the interradials are complete and rudiments of some of 
the remaining sixteen, those adjacent to the primary adradials, are 
noticeable. All or nearly all of the tentacle bulbs of the fourth series 
have tentacles and all or nearly all of the bulbs for the fifth series 
have put in an appearance. There are no lithocysts adjacent to these 
yet. The lips appear as sixteen lobes, each notched slightly. 
In the majority of specimens the development becomes more 
irregular as it proceeds but one specimen, 27 mm. in diameter, was 
found, developed so symmetrically that all of the canals of the fifth 
series were present in whole or in part and none of the sixth series 
had started. As there were thirty-two in the fifth series, the whole 
number was exactly sixty-four. All of the tentacle bulbs of the fourth 
series have tentacles but none of the fifth series although all of the 
bulbs of this series are more or less developed and each of them has 
a pair of lithocysts at the base. The lithocysts, therefore, now num- 
ber one hundred and twenty-eight. The lips consist of the sixteen 
lobes as in the preceding but instead of the single notch in each, one 
or two others give the iobe a more or less wavy appearance. 
Usually the irregularity is such that before some of the latest of 
the fifth series of canals have completed or even in some cases before 
they have started to form, some of the sixth series may have started. 
These come in very slowly and in no case have I seen the set complete, 
although many medusæ up to 65 mm. in diameter were examined. 
In the adult medusa, 75 or 80 canals seem to be about the upper limit. 
In the development of the canals of the sixth series, the same order 
is followed as in the fifth series, i.e., those adjacent to the perradials 
appear first, then those adjacent to the interradials, those adjacent 
to the primary adradials and those adjacent to the canals of the fourth 
series. Although in very few cases have I seen any of the last of 
these developed. The tentacle bulbs of the fifth series may all develop 
tentacles although in few cases is the set entirely complete. Tentacle 
