3o6 



DISCOVERY REPORTS 



naked specimens is very diflrerent from that of the grain-covered ones, there can be no 

 doubt that they are only individual variations, the other characters being identical, and 

 all intermediate stages being found. The supplementary dorsal plate may be very 

 regularly developed, or it may be found only here and there (Fig. 33 b, c). The lateral 

 plates may leave a space between them in the ventral midline, but the ventral plates 

 remain just as widely separated as where the lateral plates join completely. 



The genital slits vary somewhat in length, but they hardly exceed a length of 

 0-5 mm., and are often only half that length; there may be some granules at the 

 slits. The adoral plates are excluded from the genital slits. The arm spines are three 

 or four. 



This species is viviparous and hermaphrodite, but not a protandric hermaphrodite. Even 

 at a size of 3 mm. diameter the gonads are hermaphrodite. In such young specimens 



Fig- 33- Opbiolebella biscutifera (G. A. Smith). Part of oral side {a) and dorsal side {b-c) of two 

 different specimens, one without, the other with granules, xio. 



there is only one gonad in each bursa, placed at the interradial side. At a size of 4 mm. 

 diameter also an adradial gonad is present ; this latter gonad would seem to be male at 

 first, the young eggs appearing therein a little later than the sperm cells. At a diameter 

 of 7 mm. there are two gonads at the interradial, one at the adradial side of the bursa, 

 all of them containing both male and female genital products. At this size young ones 

 are found in the bursae ; I have found no more than three young ones in a specimen, but 

 of an extraordinary size, up to 2 mm. in diameter of disk. It is difficult to imagine how 

 such large young ones can get out through the minute genital slits, only 0-5 mm. long. 

 What a squeezing they must undergo, in spite of their rather large, compact scaling. 

 It would seem difficult enough for an arm alone of the young one to come out through 

 the small slit — but such a large disk, and five radiating arms! It always makes one 

 wonder, seeing the young ones in the bursae of viviparous Ophiurids so jammed to- 

 gether and distorted, how they can get clear of each other and assume normal radiate 

 form. But the present case certainly seems to represent the climax of birth-difficulties 



