ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
477 
Tlio pore-canal is formed from endodcrmal and ectodermal elements, 
and not as in Antedon (Bury), by the perforation of a single elongated 
cell. The stage with two bilaterally symmetrical pores does not 
appear to be pathological, but to be a definite stage in the ontogeny of 
Asterias , and to have a phylogenetic significance. 
On the whole, this investigation tends to strengthen the view that 
the bilateral larval form of Echinoderms is ancestral and not secondarily 
acquired. 
Early Stages of Echinoderms.* — Prof. W. K. Brooks found that 
normal, vigorous starfish larvae have the water-system at first bilaterally 
symmetrical in every particular, though the right water-pore and pore- 
canal degenerate and disappear very early. Soon after the appearance 
of the ciliated bands there is, on each side of the stomach, an ingrowth 
of ectoderm, so that, later on, each enterocoel has a fully developed canal 
to the exterior, though the right one degenerates and disappears, while 
the left migrates towards the middle line of the body. The author 
thinks that this phenomenon furnishes a strong argument in favour of 
the view that the larva is ancestral, for a bilateral structure which loses 
its symmetry almost at the beginning of locomotor life cannot be an 
adaptation to locomotion. 
The resemblance between the paired pore-canals of these larvae and 
such structures as the spiracles of Appendicular ia and other Tunicate 
larvae is worthy of note, for in both cases paired ectodermal involutions 
meet and fuse with diverticula from the digestive tract. 
Starfishes collected by the ‘ Hirondelle.’f — Prof. E. Perrier has a note 
on the starfishes collected by the Prince of Monaco in the Atlantic. Of 
the thirty-three species nine are new. Of these, four are types of new 
genera, and for them there are proposed the names Prognaster Grimaldii , 
Caly caster monoecus, Scleraster Guernei, and Hexaster obscurus. Prognaster 
has a dorso-central, five small underbasals, five large basals, and the 
first radials or “ carinals.” Calycaster is remarkable for the simplicity 
of its skeleton. Hexaster is one of the Pterasteridae, allied to Marsipaster 
and Calyptraster , and is remarkable for having six arms, and a convex 
and relatively resistant dorsal surface. 
Classification of Holothurians.J — Prof. H. Ludwig, after giving a 
detailed account of Anhyroderma musculus, a Molpadiid from the Medi- 
terranean, discusses the arrangement inter se of the groups of Holo- 
thurians. He takes notice of various organs of the body, such as the 
tentacles, the corpuscles in the skin, musculature of the body-wall, 
retractors, calcareous ring, tentacular canals and ampullae, stone-canal, 
intestine, branchial trees, Cuvierian organs, gonads and blood-vascular 
system. A review of all these leads to the conclusion that the Molpa- 
diidae are most closely related to the Dendrochirotae ; the presence 
of retractors, the structure of the stone-canal, the arrangement of the 
muscles of the wall of the intestine, and the feeble development of ten- 
tacular ampullae indicate the affinity of the Synaptidae to these other 
two groups. Prof. Ludwig believes that there was a primary dendro- 
* John Hopkins Univ. Circ., x. (1891) p. 101. 
f Gomptes Rendus, cxii. (1891) pp. 1225-8. 
X Zeitbchr. f. Wiss. Zool., li. (1891) pp. 569-612 (1 pi.). 
