74 University of California Publications in Zoology. L VoL - 6 



seen that there is less variation here than in cither the number 

 of branchial tentacles or dorsal languets. 



The Branchial Sac. 



The disposition and size of the dorsal languets is noteworthy. 

 Plate 12. fig. 14, d. I., shows the typical state of things for a 

 small animal (1.25x1.5x1). The wide, hare area to the right 

 .1 indicates anterior, and the piece of sac is. of course, seen 

 on its inner surface), between the series and the stigmata, and 

 the entire absence of such an area to the left, attracts attention 

 first. Although areas of this nature are not uncommon in the 

 Cynthiidae, it is not often so broad as here. It is present, for 

 example, in //. superba (Ritter '96). These two species, so very 

 different in most respects, have another common point in con- 

 nection with the languets, viz.: stragglers occur in both outside 

 the line. ('. /'. These are more numerous in sup( rim than in john- 

 soni. They arc most apt to be on the bare area, but an occa- 

 sional one is seen in other places. Only one is present in figure 

 14. but that is especially interesting since it is on the branchial 

 membrane proper. I call particular attention to these strag- 

 glers, and raise the question, are they not. in essential nature, 

 mutants? 



In larger individuals the languets are longer ami more slen- 

 der than are those of the one shown in figure 14. I have taken 

 some pains to determine whether the languets in this species 

 correspond to the transverse vessels, or sinuses of the branchial 

 membrane, as they undoubtedly do in some ascidians. Damas, 

 i 1900), for example, has established very beautifully such a rela- 

 tion in Ciona intestinalis. Figure 14 was drawn by Miss Johnson 

 with this point especially in mind, and she has attempted to 

 assign the different languets to particular sinuses. There is, 

 however, so much departure from regularity even in so small 

 a .specimen that one cannot decide with great confidence thai 

 such a coincidence is the rule. I am inclined to believe that in 

 still smaller individuals such a rule would be recognizable. 



The investigations of Selys-Longchamps and Damas. which 

 will be noticed more at length later, have put the transverse 

 sinuses and stigmata in quite a different light both as to their 



