es 



318 NEREIS DIVEES'ICOLOR. 



except in the presence of ova, which appear most abundantly, in the sections, at the 

 bases of -the feet and extending into their lobes. The number in the cceloin is not lai 

 many, in all probability, having fallen out. The dorsal and ventral longitudinal muscl 

 show little change, the pennate fold of the latter being well developed. The oblique 

 muscles pass at each side slightly below the nerve-cord to be attached to the basement- 

 membrane ; and at least three neural canals are present, the larger lateral having a 

 coagulable fluid internally, and each runs along the outer border of the nerve-trunk 

 between the pairs of ganglia. The median or dorsal canal, again, appears to have a 

 separate strand in the interganglionic region, and when it reaches the ganglia it splits 

 into two trunks in certain sections. The muscles of the bases of the feet and of the 

 bristles are also strong. The wall of the alimentary canal appears to be of normal 

 thickness. 



The annelids remained very much in the same condition during December, the great 

 majority of those examined being females, so much so that it was at first considered 

 probable that, as authors had stated, a complex sexual condition existed (e.g., alternate 

 development of the reproductive elements) ; but as a few males were still met with and 

 no trace of an intermediate stage occurred, such complexity could not be proved. This 

 month the only difference in the sections of the females is the increase in the size of the 

 ova, the abundance of the ccelomic corpuscles, and the distension of the body-cavity 

 and the bases of the feet, so that the muscles of the wall are stretched. The vascularity 

 of the outer surface of the gut also appears to be increased. The segmental organs 

 show no feature of note. In the males the perivisceral cavity and the bases of the feet 

 contain dense masses of translucent granular cells, the large nuclei of which stain deeply 

 with eosine. 



The great increase of the large granular cells in the ccelomic cavity in January 

 is a feature of moment, especially in those females in which the ova are small. The 

 enormous masses of these cells distend the bodies of the females and they probably 

 increase by division, each being filled with spherules. In glancing at the living annelids 

 a pale, or greyish-green hue characterizes the posterior region of the body in the 

 females; whilst the anterior segments have their vascularity increased, the dorsal vessel 

 of the foot and its branches especially being distinct. When the posterior region is 

 punctured, the masses of ova have a pale greenish colour as in the previous months, 

 and are similarly unfertilized. As many have discharged ova, it would appear that 

 fertilization is external as in allied forms. 



The sexes are not always distinguished by colour, both males and females being 

 greenish or dull yellowish, though the males are often paler. No change in eyes, feet, or 

 bristles is apparent. In many an opaque, dull whitish condition occurs in the anterior 

 feet, which are filled with the large granular perivisceral corpuscles. Moreover, almost 

 all have a touch of white at the base of the dorsal cirrus— from one end of the body to 

 the other, a similar touch occurring at the tip of the cirrophore of each tentacular 

 cirrus. 



Mendthal x figures two examples, one of the general brownish-orange hue of the 



1 ' Untersucli. u. d. Mollusken u. Amieliden des frischen Haffs/ p. 9, Taf. figs. 1 and 2 (Konigs- 

 berg, 1889). 



