1907. 



Records of the Indian Museum. 



S3 



it, as Stoliczka's diagram {o-p. cit., pi. xi, fig. 2) shows very 

 clearly ; but although this holds good as a general rule, there are 

 many exceptions, which arise either from the suppression of some 

 of the tentacles of a cycle or by the appearance of supernumerary 

 tentacles. The latter phenomenon may occur in one of two ways : 

 not infrequently an extra tentacle makes its appearance at the 

 base of one already fully formed than which it is at first consider- 

 ably smaller, and less frequently a tentacle splits longitudinally 

 into two. I have seen both these methods of multiplication in 



V\G. 2. — PIxpanded disk of M. schillerianum var. exul, oblique lateral view, nat.size. 



progress in the variety, and have little doubt that they also occur 

 in the typical form, judging from the slight divergencies from regu- 

 larity which I have found in specimens. 



As regards the individual tentacles I can find no difference 

 between the two forms. In both they are elongated and tapering 

 and are perforate at the free extremity. I have on one occasion 

 seen an acontium protruded through the pore. The nervous layer 

 of the ectoderm is clearh' marked in transverse sections and the 

 layers are generalh* of t3'pical form and structure. 



The wall of the disk is thinner in the variety than in the 

 t3^pical form. In the latter, when the disk is fully expanded its edge 

 makes a right angle with the column and is entire. This is also the 

 case as regards individuals of the new race of all ages, when 

 their disks are fully expanded. When the disk of the typical form 

 is partly contracted, however a fold of the wall of the column 

 containing the upper extremity of the sphincter makes its appear- 

 ance, and this is also the case in young individuals of the new 

 race less than about 2 cm. long. Even after the appearance of this 

 "collar," the margin of the disk is entire. In larger individuals 

 of the isolated race, for reasons to be di.scussed immediately-, the 



