. Bulletin - United States National Museum. Science. 150 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. In the transitional pinnules the characteristics of the genital pinnules first appear at the distal end and rapidly extend inward toward the base. These intermediate pinnules are followed by from 3 to 35 or more pinnule pairs (usually from 10 to 20) upon which the perfected gonads are developed (figs. 281, 282, p. 215). The firet commonly bears a relatively small gonad, but on the second and following this rapidly increases and soon reaches its full size. After the middle, or the proximal two-t
. Bulletin - United States National Museum. Science. 150 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. In the transitional pinnules the characteristics of the genital pinnules first appear at the distal end and rapidly extend inward toward the base. These intermediate pinnules are followed by from 3 to 35 or more pinnule pairs (usually from 10 to 20) upon which the perfected gonads are developed (figs. 281, 282, p. 215). The firet commonly bears a relatively small gonad, but on the second and following this rapidly increases and soon reaches its full size. After the middle, or the proximal two-thirds, of this pinnule series the gonads com- monly begin gradually to decrease in size, finally disappearing altogether. The gonads arise on the third seg- ment and extend outward for a variable distance over from 2 to 20 (usually over from 5 to 10) segments. They are of two distinct types, each of which has a more or less definite range (1) a short abruptly rounded type (figs. 281, 282, p. 215) occun-ing in almost all of the species of the Macrophreata, in the majority of the Charitometridae, and in certain of the small 10-armed species of Comasteridse, and (2) a long fusiform type, found in the Tropio- metrida*, most of the Thalassometridse, and in large individuals of large species in certain macrophreate genera. Both types are found in the Heliometrinse, though the second is greatly pre- dominant, and both types are found in Antedon hifda and A. petasus, though only the second in Antedon 'mediter- ranea and A. adriaticn. The genital pinnules are, with but few exceptions, shorter than the oral pinnules, and usually very much shorter. The first four or five pairs are of equal, or nearly equal, length; on the following the length slowly and gradually increases, coincident with the decrease in the size of the gonad, until the outer genital pinnules merge imperceptibly into the distal pinnules. The transition from the middle to the distal type of pinnule begins first at the dis
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