ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 245 



developed state the yolk-gland is formed of distinct cells ; ordinarily only 

 one egg is developed, and one gonad is ripe before the other. 



Tornaria and Balanoglossus.* — Mr. G. B. Haldeman describes a 

 Tornaria occurring on the Atlantic coast of America. It resembles that 

 described by Metschnikoff, in being opaque, having eye-spots, and having 

 the pore of the water- vessel on the left side. 



The transformation of this larva was traced out, and the young 

 Balanoglossus is only one-half the size of the Tornaria. It appears 

 probable that it is the young of B. BrooTcsii. The author considers the 

 homology between the water-vessels in this larva and in Bipinnaria to be 

 true, and as justifying Metschnikoff 's view of the relationship between the 

 Enteropneusta and Echinodermata. But whether Tornaria or Bateson's 

 larva (B. koivalevsMf) is to be considered as more nearly representing an 

 ancestral type, there is still the possibility that each may possess certain 

 phylogenetic characters that have become obsolete in the other. 



Echino dermata. 



Holothurioidea of the 'Blake' Expeditions.! — Dr. H. Theel gives an 

 account of the Holothurians dredged in the Gulf of Mexico, in the Carib- 

 bean Sea, and along the eastern coasts of the United States ; the author 

 wishes it to be regarded as an appendix to his recently issued ' Challenger ' 

 report ; he describes several new species, but no new genera, and makes no 

 general remarks. 



Development of Generative Apparatus of Echini ds.j: — M. H. Prouho 



reports that young individuals of Strongylocentrotus lividus, measuring 

 1 to 1 • 5 mm., have no genital pores or apparatus ; the madreporic plate is 

 pierced by two or three aquiferous pores and the sand-canal is well developed. 

 Along this canal and supported by the same mesenteric layer there is an 

 elongated cellular mass, which is the rudiment of the ovoid gland. In 

 individuals of 3 mm. diameter, the genital plates are still imperforate, but 

 the genital apparatus has begun to be formed. Delicate sections made 

 parallel to the axis of the test reveal the existence, near the apical 

 extremity of the growing ovoid gland, of a bud limited by a very distinct 

 membrane. This bud, which will give rise to the whole genital apparatus, 

 contains large nuclei. As the young urchin grows the bud developes, 

 advances under the madreporite, and then prolonging itself under the other 

 genital plates, makes the tour of the periproct. Opposite each interradius 

 the ring thus formed gives off a prolongation in which the large nuclei, 

 characteristic of the primitive bud, are always found. This is the condi- 

 tion of things in examples 6 mm. in size, and the genital apparatus may 

 now be said to consist of five interradial buds connected with one another, 

 and with the mesentery which supports the ovoid gland by a membranous 

 circumanal ring. In individuals a little older, the five buds may be seen 

 to give off small lateral ramifications, while their aboral end approaches 

 and soon perforates the proper genital plate. 



If this bud is given off from the ovoid gland the development of the 

 genital apparatus of Echinids is effected by a process analogous to that 

 described by Prof. Perrier in the Comatulidse ; it might be said that the 

 growing gland is, or contains, a genital stolon like the dorsal organ of young 

 Comatulids ; but the author does not take this view. It is true that the 



* Johns-Hopkins Univ. Circulars, vi. (1886) pp. 44-5. 



t Bull. Mus. Comp. Zool. Cam-bridge, xiii. (1886) pp. 1-22 (1 pi.). 



X Comptes Rendus, civ. (1887) pp. 83-5. 



