BIHANG TILL K. SV. VET.-AKAT). HANDL. BAXD 13. AFD. IV. N:0 5. 85 



space, closed abovc and below by older converging series. 

 A remarkable exception from this mode of increase sometimes 

 occurs in virtue of whicli a new adventitioiis vertical series 

 of tubercles is added, not on the disk, near tlie middle siiture, 

 but at the margins, externally, along a line closely bordcring 

 upon the zone of the ambulacrum. Troschel was the first 

 to observe this in the aiithentic specimen of old Klein's Ci- 

 daris assulata pustuh^sa /?, that lay before him as now before 

 me, and it is readily seen also, and more developed, in the 

 largest of the Linnean specimeus of A. iixula L., Tah. T ■,pg. 1, 

 and, in a bcginning state, in a specimen of A. Dufresnei Bly. 

 Outside the first, primordial, series, betweeu it and the suture, 

 an adventitious vertical series is forming, not proceeding from 

 the base and continuing iipwards, biit at tlie middle part of 

 the height, where there is more room, somewhere from the 

 sixth plate, or so, to the twelfth or foiirteenth, or there- 

 aboiit, and not going on continuously, with a tubercle on every 

 plate, but interruptedly, as shown by the following tables. 



Cidaris asf3ulata pusta- a u • r- it » u • 7-> ^ -D^rr 



, j „ ^ Arbacia Lixula L. Arbacia Uuiresnei Blv. 



lösa (i Klein. 



1234.') 123 4 5 12345 



a b a b a b a b a b a b a b a b a b a b a b abababab 



12 — • 12 12 12 12 



11 11 11 11 — 11 -11 — 11 — 11 



10—10- 10 1010 10 10 — 10- 



9 9 9—9-999!» 9 



888 88 88 88— 8—8 8 8 — 



7 7 7 



C, 6 6 6 — — 



It is seen that the plates 8 to 12 bear the greater number 

 of these tubercles. They are always smaller on the upper 

 plates, and each of them appears at first above the primordial 

 tubercle upon a marginal expansion of the plate, and then 

 slides down into its proper place in the transverse row and 

 there attains the normal size. They are seen nowhere in the 

 young and are few and minute in the half-grown animal, while 

 in nearly adult specimens they have increased in size and 

 number and gradually are filling tlic vacant places. At last, 

 it may therefore be supposed, in old specimens a complete 

 series of these »wisdoiiD-tubercles will have been broucrht about 



