MUSEUM OF COMPAKATIVE ZOOLOGY. 83 



origin in the embryo, the formula would have to be written somewhat 

 differently ; namely, thus (16) : — 



•{^C-$- c* b* a* B-r-j- d* c* b* a* A^s-e* d* c* b* a* a* 7* fi* a* [A] 



In a species of Pennaria, common on our coast, which is probably 



Pennaria tiarella, McCready,^ I have noticed the presence of a similar 



law of budding. The whole stock lies in one plane, the lateral branches 



arising alternately from the right and left of a central stock, like the barbs 



of a feather. These lateral branches give rise to a series of secondary 



ones, which are all placed on the same (axial) side of the branch. Each 



branch, of whatever degree, originates as a bud bearing a polyp. From 



the elongating stalk of this terminal polyp, buds arise, — the beginnings 



of branches of the next higher order. The stock may be represented by 



the following formula : — 



A 

 m 



d * — 



I 

 c* 



a I 



b* I 



a I 



;8 * I 



C ^ _*_| ^1 



I ^* I 



(17) ^D 



I 

 a * 



I 

 b * — 



I 

 c» 

 * 

 B 



Expressed in a linear series, this formula may be written : — 



(18) •i5jD*C*B*c*b*a* A*d*c*b*o»a*/3»a* 



which is identical in form with the second formula (16) given for Hali- 

 stemma. 



1 This species is figured by Leidy ('55, Plate 10, Figs. 1-5) and Verrill (73, Plate 

 XXXVII. Fig. 277). An allied species, P. gibbosa, is figured by Louis Agassiz 

 in the " Contributions" (Vol. III., Plate XV. Fig. 1). In describing P. Carolinii, 

 Weismann (Entstehung der Sexualzellen, p. 122) says that the lateral hydranths 

 do not possess the capacity of giving rise to new lateral hj'dranth-buds (of a higher 

 order). But, as indicated above, P. tiarella seems to do this regularly. Leidy's 

 and Verrill's figures show the same thing. 



