NEREIS DIVEBSICOLOR. 317 



that in most Polychasts the fertilization and development of the eggs occurs in the 

 interior of the mother, there seems to be very slender foundation in fact. It is true 

 Schroder states that in sections he has found the morula-stage of N. diversicolor in 

 the body-cavity, but the complex condition of things in this species before, at, and after 

 reproduction might well lead to misinterpretation. Schroder, at any rate, could not find 

 the later stages in April and May. Mendthal described the species from the Bay of 

 Pillau as carrying both eggs and testes in June, and he was the more inclined to believe 

 in its hermaphroditism since Schroder met with only three males out of forty-eight 

 examples. He places and figures the testes in the dorsal region as pear- or flask-shaped 

 masses to the exterior of the dorsal longitudinal muscles. The supposed testes, therefore, 

 occupy the same position as the outer limb of Dr. Goodrich's dorsal organ, and it may be 

 that the cilia were a source of misapprehension. On the other hand, he describes the ova 

 as developing at the bases of the feet, the figure representing them in the position of the 

 segmental organ. 



De St. Joseph, however, could not corroborate the foregoing observations. Gravier, 

 on the other hand, considers that hermaphroditism and viviparity may exceptionally exist 

 in this form, and in the ' Cambridge Natural History ' it is stated that viviparity is 

 characteristic of it, whilst Goodrich 1 quotes it as a viviparous hermaphrodite along with 

 " Salmacina Dysteri and Pomatoceras triqueter." 



The annelid is very common on many parts of the British shores, burrowing in clay, 

 sand, mud, peat, and similar media, and at St. Andrews it abounds at the upper end of 

 the harbour amidst muddy clay on the sides of the Kinness Burn which enters there. 

 Careful observations were carried out lately to test the condition as regards repro- 

 duction ; yet though both hermaphroditism and viviparity have been discountenanced, 

 it has not been possible to find the worm either discharging from its tunnel in the mud 

 its eggs and sperms or becoming pelagic at maturity and thus dispersing the sexual 

 elements. So far as can be observed, the former, perhaps, seems to be the more likely, 

 though no certainty exists on this head. 



In the middle of October the majority of the examples — both large and small — are 

 females with fairly developed ova, which are almost visible to the naked eye and easily 

 under a lens. In these the vascularity of the feet has slightly increased, but no change 

 in the lobes of the feet or in the bristles has occurred. Amongst the ova in the ccelomic 

 space are numerous pale granular cells, apparently modified perivisceral corpuscles. Very 

 few males are obtained at this time, and these for the most part are undeveloped. 



In November comparatively few ova are attached to the ventral plexuses, most 

 being free in the perivisceral space. On the other hand, the vascular plexuses in the 

 region of the ciliated organ are laden with dense groups of rather coarsely granular cells, 

 sometimes in lobular masses, and it is considered that these pale cells are associated 

 with the growth and maturation of the ova in the ccelomic space. The ova increased 

 considerably in size towards the end of the month. 



In transverse section 2 the body of the annelid at this time differs little from the type 



1 ' Journ. Linn. Soc./ vol. xxviii, p. 107. 



3 I am indebted to Dr. Tosh, Assistant Professor, for valued aid in making these sections and in 

 other respects. 



