DEVELOPMENT OF THE ANOPLA. 123 



the segmented condition of the body, and assumes the outline of a Nemertean, that is, has an 

 elongated vermiform body without segments or appendages, a head furnished with two large 

 eyes, and a mouth apparently opening behind the ganglia. The observations at present recorded, 

 however, are not sufficiently decisive to satisfy us. Thus no mention is made of the important 

 fact as to the presence of cilia on the general surface of the body, both before and after the 

 shedding of the anterior and posterior circlets of long cilia. While it is true no bristles or other 

 diagnostic structures connecting the form with the majority of the higher Annelids appear, it is 

 equally evident that the essential Nemertean anatomy is wanting. Nothing is said of the 

 characteristic cephalic ganglia and sacs, the lateral nerve-cords, the proboscis, or the structure of 

 the cutis — points that are recognized in every known Nemertean long before it has reached the 

 development and age of A. Agassiz's form. The latter thinks, also, that it approaches the Nareda 

 of Stimpson, but this is doubtful, since the somewhat meagre description and the figure would 

 indicate Nareda superba to belong to the division of the Enopla, whereas the young form has 

 its mouth apparently opening behind the ganglia. Our judgment must therefore be reserved 

 with regard to the particular type to which this interesting animal belongs. 



The development of Carinella has not yet been observed. 



In Cephalothrix the ova and spermatozoa are developed in a dense series of sacs (that give 

 the animal a transversely barred aspect), which commence a short distance behind the mouth and 

 continue nearly to the tip of the tail. The males are distinguished by their somewhat pale aspect 

 when the reproductive organs are fully developed, viz. towards the end of January and during 

 the subsequent months of spring. The spermatozoa (Plate XXI, fig. 13) consist of short 

 flattened spindles with rounded instead of pointed ends, that to which the tail is attached being 

 somewhat smaller than the other. In swimming the two ends appear as clear dots. Though 

 the animal is extremely elongated, the bodies of the spermatozoa are comparatively short. The 

 mature female presents a dusky or slightly fawn-coloured aspect, the ova, under' gentle 

 pressure in the living animal, being arranged in dense transverse rows in each ovary. The 

 total number of ova produced by a single example must be very great. In transverse sections 

 they occupy a large ovoid space on each side of the alimentary canal, upwards of twenty ova — 

 very prettily arranged in a concentric manner — occurring in a single thin slice. The space of the 

 digestive canal in these preparations had thus assumed the form of the letter x, the walls 

 approaching each other in the middle, but diverging superiorly and inferiorly ; while a wedge- 

 shaped fold from the dorsum below the proboscis, and another from the ventral surface, 

 completed the resemblance. This was the more marked if the proboscis had been ejected. 

 The ova are deposited from the beginning of February till June ; either adhering together in 

 irregular masses by their edges or a little accidental mucus, or scattered about the vessel 

 in detached groups. In several instances, however, they were enclosed in a translucent 

 sheath of mucus. On deposition they have a granular structure throughout (Plate XXIII, 

 fig. 12), with a clear spot and globule,; and measure about yioth of an inch in diameter. The 

 ova pass rapidly through the usual stages, and on the 11th February the embryos revolve 

 actively in the egg by aid of their cilia, and in some cases are hatched. The extruded 

 animal (Plate XXIII, fig. 13), under moderate pressure, has a globular form, but assumes 

 various shapes when free, the ordinary one being that of an apple — the long ciliary process 

 representing the stalk, while the body slightly tapers towards the posterior end. It is opaque 

 and granular, with the exception of the margin, which is somewhat translucent, from the slight 



