ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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rhabdite-“ cells.” The latter secrete a homogeneous sphere which 
becomes split up into numerous rods or rhabdites, which are discharged 
to the exterior. The two structures together must be regarded as 
equivalent to the rhabdite-cells of the Turbellaria ; for the non-nucleated 
bodies are probably dissociated parts of the basal cells. The bulbous 
enlargements of the plumes are therefore to be regarded not as sense- 
organs but as rhabdite-batteries. 
Sexual Phases of Myzostoma.* * * § — Prof. W. M. Wheeler criticises 
Beard’s conclusion that Myzostoma glabrum is dimorphic, and that the 
species is represented by hermaphrodite individuals and by dwarf 
“ complemental males ” attached to the dorsal surface of the large 
hermaphrodite individuals which adhere to the peristome of Antedon 
rosacea. 
Wheeler’s position, which Beard has criticised, but to which the 
author firmly adheres, is “ that M. glabrum is monomorphic, each in- 
dividual of the species being from the first hermaphrodite, i.e. possessing 
both ovaries and testes, and being, like other members of the genus 
(notably M. cirriferum and M. alatum ), protandric, then hermaphrodite, 
and ultimately more or less hysterogynic. In other words, the functional 
male phase (Beard’s * complemental male ’) passes into the functional 
hermaphrodite phase as soon as the first ova mature, and the functional 
female phase begins with the atrophy or disappearance of the testes. 
The cysticolous and entoparasitic species of the genus tend towards 
a condition in which the functional male and female phases overlap 
but little, thus exhibiting only a brief functional hermaphrodite phase 
(M. eremita) ; or these phases no longer overlap, and thus present two 
well-marked periods of sexual maturity, one male and the other female 
(M. pulvinar ).” 
North American Fresh-water Bryozoa.j — Dr. C. B. Davenport 
begins a series of proposed systematic synopses of North American 
Invertebrates with a key for the determination of the Bryozoa. In under- 
taking this useful piece of work, the American Naturalist promises to 
determine and return any specimens that cannot be placed in the keys, 
and solicits correction and criticism for future revision. 
Development of Orthonectids.J — MM. M. Oaullery and F. Mesnil 
discuss in particular the “ plasmodial sacs” of Stoecharthrum giardi 
Caull. et Mesn., which they regard as expressing a phase of asexual 
multiplication after the parasite enters its annelid ( Scoloplos ) host. 
They agree in a general way with Giard in comparing the plasmodial 
sacs to sporocysts in Trematodes. More exactly, however, the plas- 
modial sacs are comparable to the axial cell in Dicyemidae. 
Echinoderma. 
Development and Anatomy of Synapta vivipara.§ — Mr. H. L. Clark 
has made a series of detailed observations on this curious form, which 
* Zool. Anzeig., xxii. (1899) pp. 2S1-8. 
f Amer. Nat., xxxiii. (1899) pp. 593-6 (3 figs.), 
j Comptes Rendus, cxxviii. (1899) pp. 516-9. 
§ Mem. Biol. Lab. Johns Hopkins Univ., iv. (1898) pp. 53-88 (5 pis.). 
