710 MR. L, A. BOBBADAILE ON TlIK SPAWN [Dvr . 17, 



Several of these 8 pawn-masses wen- brought in a vessel of water 

 to the rest-house at Kankesanturai, where, when they had been 

 placed in shallow glass dishes, u number of larvae hatched out of 

 them and passed through the successive stages of their develop- 

 ment until, as T was on the point of leaving for the south of the 

 island, the observations were unfortunately broken olf. The 

 progress of the larva? was, however, so rapid that, starting as 

 spherical ciliated objects, they had, in the few days during which 

 they were under observation, assumed a completely worm-like 

 appearance. Their history, which I. propose to describe in as 

 great detail as my information will allow ', shows an interesting 

 feature in the secretion by the larvae, after they have for some 

 time been free-swimming, of a second mucous matrix, in which 

 they live gregariously, much as some caterpillars do in the web 

 which they spin. 



1. The youngest embryo observed ( PI. XXXIX. fig. 3) was very 

 nearly spherical in shape, about "2 mm. in diameter, without eye- 

 spots or cilia, and almost filled with a mass — presumably endo- 

 dermal — of protoplasm containing yolky granules and droplets. 

 Viewed with reflected light, this mass was yellow while the outer 

 layer was white. The whole was enclosed in a thick radially- 

 striated membrane. 



2. To these succeeds a stage (PI. XXXI X. fig. 4) in which the 

 young, while still enclosed in the spawn-mass, develop two eye- 

 spots in the anterior half of the sphere and a complete covering of 

 cilia, by means of which they rotate in the mucus. The cuticle 

 is thinner and its striation is less obvious. This " atrochal " or 

 " holotrochal " stage resembles the pelagic larva described by 

 (Crohn and Schneider (5) as probably belonging to a Eunicid. 

 The body of the latter larva, however, was more elongate, and 

 the apical tuft longer. 



.">. A! the liatching-stage the young larva (PI. XXX IX. fig. .3) 

 is oval, with a broad anterior end and a somewhat narrower hinder 

 end. Kouncl its middle is a broad ciliated band, separated by a 

 narrow gap from a tuft of longer cilia at the apical pole and by 

 a wider gap from a patch of medium length at the hinder end. 

 These are the characters of Haecker's " Prototrochophora," which 

 thus follows an atrochal stage in the present instance. In front, 

 just within the anterior boundary of the ciliated band, is on each 

 side a conical black eye-spot, with the apex of the cone directed 

 backwards and inwards and its base hollowed for the reception of 

 the — as yet indistinct — refractive body. The greater part of the 

 interior of the body is filled by a yolky mass — the rudiment of the 

 future mid-gut, — but at each end i* a clearer granular area. The 

 mid-gut rudiment projects backwards in the axial line towards 

 the anal region, with which it seems to be already in connection 

 by a narrow non-yolky passage, although, as no outward opening 



1 The same accident which deprived me of specimens <>i the aduil worm 

 having also destroyed my preserved material of the developmental stages, f am 



nni I'l'- t" ileal with any but the outward features of the young and those 

 which may lie seen, when they are mounted whole, as transparent objects. 



