NEPHTHYS GMCA. 15 



An early stage is described and figured by Claparede and Mecznikow in the form of 

 the usual trocophore. It is pear-shaped without trace of segmentation, and with a ring 

 of cilia in front of the mouth, and a pencil of cilia anteriorly at the apex- The 

 alimentary canal bends forward toward the sensory area anteriorly — the dilated region 

 being greenish — and then curves backward to the conical posterior end. A brown 

 eye-spot is on each side. 



Both Claparede and Mecznikow, and Hacker, describe and figure the next stage. 

 Hacker (1896) gives the first metatroch stage of Nephthys scolopendroides as some- 

 what pear-shaped with a green-flecked anterior end and a pair of eyes. Two brown 

 pigment-lines occur behind the prototroch, and green and red pigment behind the 

 paratroch. The stomodeum is transverse with a three-lobed upper lip. The mid-gut has 

 brown and blue pigment and oil globules, and the anus has blue pigment. This author 

 finds that the prototroch has an upper small and two lower streaks or grooves (Reifen). 

 The paratroch is one-rowed. The sides of the larva are crenate (four segments), but 

 without bristles in one elsewhere procured. 1 



A stage in which the large globules of yolk occur far forward, just behind the eyes, 

 is given (Plate L, fig. 1). ISTo colour is present. Short bristles are distinct in three 

 segments, and they do not yet show the transverse strise. Round diatoms occurred in 

 the alimentary canal. The madder-brown tip to the tail is more diffused, not clearly 

 forming two bands. The mouth in the sketch is on the under surface, so only the 

 large globules are seen. In a larval form with eight bristled segments (Plate L, 

 fig. 2) the head is broad and horseshoe-shaped, with a general pinkish-yellow hue, 

 and two madder-brown eyes. The proboscis is indicated behind — as far as the 

 commencement of the second body-segment. The alimentary canal following has 

 numerous large clear globules, and terminates posteriorly in a narrow rectum, and a 

 vent at the median short style. The colour of the gut is bluish-green. Two boldly 

 ciliated regions are present — the preoral and anal. The latter is marked by a double 

 madder-brown band — one on each side of the cilia. A short foot behind the head bears 

 the first bristles, and thereafter seven pairs occur. At the side of each segment is a 

 small foot-lobe. The larva swims actively by aid of its cilia. The lateral bristles are strong 

 and have the characteristic transverse markings of Nephthys. Diatoms and debris were in 

 the alimentary canal. In Fig. 3 is an example captured a few days later (28th October) 

 in which the general form of the head and body has undergone alterations. 



Two later stages are figured and alluded to by Claparede and Mecznikow, one in 

 which there are eight pairs of feet, eyes with lenses, and teeth in the proboscis. Both 

 rings of cilia persist. In the more advanced stage the body is elongate and the preoral 

 ring of cilia less distinct. The characteristic bristles occur on the feet. The authors 

 suppose that the species is Nephthys scolopendroides — a common one at Naples. 



The older stage, of date October 28th (Plate L, fig. 3) presents a more distinctly 

 differentiated head, which is separated from the peristomial segment, and the area of the 

 proboscis is clearly outlined. The greenish-blue colour of the intestine is still conspicuous. 

 Though only nine pairs of bristle-tufts occur, the form is considerably older than that 



1 Plankton Exped. ' Pelagic Polych./ p. 10, taf. i, fig. 4. 



