ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
531 
leave the spot where they have settled. Then there are cyst-producing 
species which form galls or swellings on the discs or arms of their 
Crinoid host, and, lastly, some species — the endoparasitic — inhabit the 
alimentary tract of their hosts. 
All the species of these various groups may be arrauged in a series 
of increasing parasitism, from the primitive and most typical forms of 
the first group to the very aberrant species of the fourth. The departure 
in the adult from the juvenile condition increases in a corresponding 
manner. Nine species, representing every one of the groups, are con- 
sidered in the present memoir ; three of them are new. Though 
parasitic itself, Myzostoma is infested with parasites. Nansen has 
already reported the presence of a tapeworm, and Prof. Wheeler has 
found an Amoeba and a Distomum. 
The author deals at some length with the criticisms of Dr. Beard, and 
then proceeds to a consideration of the relationship of the Myzostomata 
to the Chaetopoda. He deals with the relations of the reproductive 
organs to the body-cavity, the structure of the ovaries, the nephridia, 
the segmental sacs (or suckers), the parapodia, and the cirri ; and, lastly, 
he urges that the Chaetopod affinities of Mijzostoma are further shown by 
their resemblance to the genus Sjpinther. 
With regard to the sexual condition of Myzostoma, four distinct 
stages may be recognised in their life : — (1) A phase of sexual neutrality, 
or indifference ; (2) a protandric phase extending from the appearance 
of the first ripe spermatozoa to the appearance of the first ripe ova ; 
(3) an androgynous or functionally hermaphrodite phase, extending 
from the appearance of the first ripe ova to the disappearance of the last 
ripe spermatozoa ; (4) a hysterogynous phase, extending from the dis- 
appearance of the last spermatozoa to the disappearance of the last ripe 
ova, an event which is very probably not attained at the time of the 
animal’s death. 
Echinoderma. 
New Genus of Liassic Echinoidea.* — Dr. J. W. Gregory describes, 
under the name of Archoeodiadema, a new genus of Liassic Echinoids. 
The fauna of the English Liassic is not rich in species, and as a rule the 
specimens are small, but it is of interest, as its members are primitive 
in character, and as they foreshadow many of the main lines of evolution 
followed by the rich echinoid fauna of the Oolites. The new genus 
appears to be the simplest known form of the Diadematinae ; specimens 
seem to be fairly abundant, and are generally about the same size ; 
their general appearance suggests that they are adult. 
Ophiurids of Recent Expeditions.!— Prof. R. Koehler has a short 
notice of the twenty-five species collected by the c llirondelle,’ and the 
twenty-three species collected by the ‘ Princess Alice.’ Several of the 
species are new, but do not appear to be of any special interest. 
Coelentera. 
Classification of Alcyonaria.f— Prof. S. J. Hickson called the 
attention of the zoologists at Leyden to his proposed classification of 
* fe Geol. Mag., iii. (1896) pp. 317-9 (1 fig.). 
f Mem. See. Zool. France, ix. (1896) pp. 203-13 and 241-53. 
X Report of the 3rd International Congress of Zoology, 1896, pp. 352-6. 
