The Journal of experimental zoology . a, Hydroides. The description given above for Hydroides (p. 21) is sufficientas a general characterization of this type. The functional oper-culum may be either on the right or on the left side, the rudimen-tary operculum in each case occupying the opposite position. Theopercula are not in the line of the branchiae but occupy a position ^According to de St. Joseph (94) the functional operculum appears on the left side and the rudimen-tary, his pseudopercule, on the right. He does not mention the possibility of the reverse specimens which I
The Journal of experimental zoology . a, Hydroides. The description given above for Hydroides (p. 21) is sufficientas a general characterization of this type. The functional oper-culum may be either on the right or on the left side, the rudimen-tary operculum in each case occupying the opposite position. Theopercula are not in the line of the branchiae but occupy a position ^According to de St. Joseph (94) the functional operculum appears on the left side and the rudimen-tary, his pseudopercule, on the right. He does not mention the possibility of the reverse specimens which I examined at Naples showed a preponderance of .the right-handed condition.(See p. 32.) Compensatory Regulation. 27 dorsal to the first dorsal branchiae or to the interval between thefirst and second dorsal ones. Serpula differs from Hydroides inthe entire absence of the secondary group of processes in the oper-culum (Fig. 6g). Crucigera has only four secondary processesand these are arranged in the form of a cross (de St. Joseph, 94).. Fig. 7. •Spirorhis Pagenstecheri. Ventral (slightly anterior) view showing branchiae and operculum with itsbrood chamber containing embryos ( X 40). f. Group VI. One Operculwn. No Rudimentary members of this group have only one operculum. There isno rudimentary operculum. Examples are Spirorhis, Pileolaria,Ditrupa, Filogranula (.?), Pomatoceros, Vermilia. This group may be further subdivided according as the oper-culum has a position in the line with the branchiae (Ditrupa, 28 Charles Zeleny.
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