7ii University of California Publications in Zoology. [Vol.6 



T( ntaclt s. 



The tentacle number in twenty-five individuals of //. joltn- 

 soni varied, as the t;il>)e shows, from 17 to 62, and averaged 

 aboul 42. The average for the National City five, 39.2, cannot 

 he regarded as enough less than the average fur the others to 

 he significant. In ten specimens of //. haustor the variation 

 was from 12 to 29, with an average of 21. 



Tlie branching of the tentacles is rather diffuse for the genus, 

 ami is no haphazard, lawless matter. Plate I"-', fig. 13, repre- 

 sents the whole of one of the largest tentacles of a specimen 

 l.L!.">\ l.">x 1 em. in size; i.e., one of the smallest taken in ordi- 

 nary collecting. Figure 11 shows the tip of one of the largest 

 tentacles from a specimen measuring 5x3.5x3 em.; i. <.. an 

 individual of about maximum size. The smaller tentacle was 

 1.5 mm. long, the larger 7 nun. Both were drawn by Miss John- 

 son with as much faithfulness to detail as possible. It is obvi- 

 ous that new branches are added for a considerable portion of 

 the animal's growth period. A little attention reveals several 

 laws or rules according to which these additions are made. To 

 discuss these a system of designation is necessary. The branches 

 we may call primary (&'), secondary (6"), and tertiary (6 "). 

 None of a higher grade have been observed. The axes of these 

 m,i\ be designated as follows: « axis of the tentacle itself, a' 

 axis of //. a" axis of 6". Since // " produces no branches, we 

 need not be concerned with a'". As each of these orders of 

 luaiichcs appears in different sizes (ages . such of these as are 

 referred to specifically have to be designated in some way. 

 Those branches pertaining to any given axis may well be spoken 

 of ,-is generations. Thus all the &'s may be said to belong to 

 the first generation {g') of axis a. In the same way. all the b" 

 would belong to the first veneration of the axis a. Inspection 

 of lieure 13 shows that in this particular tentacle only first and 

 second generation branches of the first order, and only first 

 generation branches of the second order, are yet present. 



Not so with the large tentacle, a part of which is shown in 

 figure 11. Here several other later generations are recognizable 

 on the various orders of axes. Thus </". </". </". also g' ". </ all 

 letters to the left), are seen pertaining to a. Also g' and g" of 



