ANNULATA. 
Verm. 19 
Anatomy and Physiology. 
Butsclili (40) does not find himself able to agree in many points with 
Robin ; he states further that the gastrula of Nephilis does not conform 
altogether either to the amphigastrula or discogastrula mode. 
Hertwig (48) studies the changes in the ovarian egg which lead to the 
condition in which it is capable of fertilization ; these are wall seen in 
Tlccmopis, where he has observed parts of the nucleolus and of tha nucleus 
go to form a new spindle-shaped nucleus. These studies are in great 
part comparative (with Toxopneustes and Rana)^ but it must be noted 
that in the Hirudinea the germinal vesicle undergoes gemmafcbn before 
fertilization, and that it is this which causes the nucleus of the ovum to 
be spindle-shaped ; the spindle-fibres are differentiated from the sepa- 
rated granules of the germinal spot. At a certain stage, the spermatic 
nucleus is found at the centre, and not, as in Toxopneuates, at the peri- 
phery of the egg. The cleavage-nucleus in all three forms is formed by 
the fusion of the nuclei of the ovum and sperm. 
Barrois gives (39) a brief account of his work on the embryology of 
Annelids at Roscoff. 
Hatschek (46) describes the development of the central nervous system 
of Lumhricus ruhellus, and concludes with some theoretical considferafcions 
on the relations between the central nervous system of the Annelida and 
Vertehrata. 
Kowalewsky makes some remarks (Arch. mikr. Anat. xiii. pp. 194-204) 
on the similarity in the early development of AmpMoxus and Lumhru 
cus, whence he concludes that the supra-chordal nervous system of tho 
Vertehrata is homologous with tho whole central nervous system of 
Vermes. 
Semper (55) discusses the gemmation of tho Naid.es, as to which no 
general formula seems possible, since variations appear to be dependent 
on season and locality. 
McIntosh (53) finds that tho blood of Magelona is densely corpuscu- 
lated, and is of opinion that this form most resembles in structure the 
Spionidce. On the circulatory system of Magelona ; id. M. Micr. J. 
xvii. p. 256. 
W. N. Ulianin is reported by Hoyer as describing the structure of 
Polygordius, and as pointing out that the only essential point of differ- 
ence between it and the Chcetopoda is the absence of setse ; that it is 
closely allied to Saccocirrus (Bobretzky) ; and that it has no relations to 
round worms (Schneider). 
Turnbull (56) points out that the difference between the ventral cirri 
of tho male and female is greatest in the posterior segments, and 
between the dorsal cirri in the anterior segments. 
The observations of Hensen (47) were chiefly on the large, deep- 
burrowing form of L. terrestris ; he concludes that (1) it equalizes the 
distribution of nutrient material by removing leaves, &c., from the 
influence of the wind, (2) it aids in the conversion of this material, (3) 
disposes it in different layers, and (4) opens up paths for and affords 
nutriment to the roots of plants [c/. Nature, xvii. pp. 19, 28, & 62]. 
