30 THE VOYAGE OF H.M.S. CHALLENGER. 



diverticula of the digestive tract. At the extreme hinder termination of the body is a 

 shallow notch, at the bottom of which is tlie anus. 



" The mouth, which is a simple opening at the apex of a small, short, conical 

 protuberance, was situate just in front of the nerve-ganglia on the ventral surface of the 

 body (it is not shown in the figure, which represents the animal from the dorsal aspect). 



" The central canal of the digestive tract terminated in front in a wide, rounded, blind 

 end, and tapered gradually to the anus at the posterior end of the body. 



" The lateral diverticula in this young specimen were evidently in an immature 

 condition, and the successive pairs showed successive stages of development, the most 

 anterior being the most fully formed. This most anterior pair is the only one which 

 shows a commencement of ramification at the peripheral extremities. The ramifications, 

 so ample and well marked in the adult worm, are seen here to be developed as egecal buds 

 from the outer ends of the long diverticula. The diverticula themselves, of which five 

 pairs w^ere present in the young sj)ecimen here figured, arise, as can be seen from the 

 figure (pi. xi. fig. 1 = P1. I. fig. 23), as simple lateral buds from the central digestive tube. 

 These buds gradually increase in length, their peripheral csecal ends being always larger 

 than the tubes connecting these with the central digestive tract, and eventually these cgecal 

 ends give ofl'buds and form ramifications. A slight enlargement in the rectum, situate 

 just anteriorly to the anus, and shown in the figure, probably represents the spot where a 

 sixth pair of diverticula were about to bud ofl^ from the digestive tube. The diverticula, 

 with the exception of the first pair, were not placed exactly opposite one another, the 

 right diverticulum in each pair being situate anteriorly to the corresponding left one. 



" The digestive tract was filled with a dark reddish-brown matter, consisting of large 

 granules and oil-globules. The contents of the diverticula were darker and more oj)aque, 

 and contained numerous clear oily globules of a bright yellow and bright red colour, 

 mingled with similar opaque globules (fig. 4, a = fig. 28). The brightly coloured globules 

 exactly resembled those of the main tract. Similar coloured globules occur in larval 

 Nemertines, and I have observed them also in a marine Planarian larva, possibly that of a 

 Thysanozoon, or the Planarian larva described by Johannes Miiller from the Mediterranean, 

 supposed to be that of Eurylepta (Clans, ' Grundziige der Zoologie,' p. 286). 



"The sac of the proboscis corresponded exactly with that described in the adult. It 

 was here found to terminate posteriorly in a blunt point at a short distance from the 

 hinder end of the body. The fluid contained in it appeared transparent and without 

 corpuscles. The proboscis itself could be carefully examined in the present transparent 

 specimen. It was without stylets and quite simple, invaginated in the usual manner ; it 

 was not seen fully protruded, but when so protruded must be slightly longer than the 

 animal's body ; it has an outer pellucid gelatinous investment, and an inner muscular 

 layer (fig. 5 = fig. 29). No retractor muscle was observed to be connected with it. 



" The nervous system consists of two pairs of ganglia, of which the upper are by far 



