

Postlarval Development of Leucosolenia variabilis, H. sp. 43 



and of L. coriacea, Mont, sp., in September. Owing to the inexperi- 

 ence with which I approached the difficult task of rearing these 

 larvae, my results are not so complete in all details as T could wish, 

 but in the case of L. variaUlis I was able to obtain a more or less 

 perfect developmental series, and in the other three species I was able 

 to make out satisfactorily the main points in (he metamorphosis, 

 especially the important question of the relation between the cell- 

 layers of the larva and those of the adult. I hope to bring my inves- 

 tigations to completion during the present year, but, in the meantime, 

 the results obtained seemed to me of sufficient importance to form 

 the subject of a preliminary note. The material which I collected 

 and preserved was further studied at Munich, in the laboratory of 

 Professor Richard Hertwig, to whom I am indebted for much kind 

 help and advice, as well as hospitality. 



The Development of Leucosolenia variabilis (Ascandra variabilis, H.). 



The larvae of L. variabilis are of the so-called amphiblastula type, 

 but in many respects more primitive than the amphiblastula larva 

 hitherto described in other Calcarea. The minute larvce (70 80 /*, 

 in length, 50 60 fi in breadth) leave the mother sponge by the 

 osculum, and at once rise to the surface of the water, where they 

 swim for about twenty-four hours. They then sink to the bottom, 

 where, after swimming about slowly for twelve to twenty-four hours 

 more, they fix themselves and undergo metamorphosis. The larval 

 life thus lasts for thirty-six to forty-eight hours. 



The oval larva (figs. 1 and 2)* is divided into an anterior region 

 composed of ciliated cells and a posterior region composed of non- 

 ciliated granular cells. The centre of the transparent larva is occu- 

 pied by a conspicuous mass of yellowish-brown pigment. The 

 ciliated cells are slender and elongated, reaching from the pigment to 

 the surface of the body. Each cell bears a single flagellum, and the 

 body of the cell is divided into an internal refractile portion and an 

 external granular portion. These two portions of the cell are so 

 distinct in the living object that a superficial examination gives the 

 impression of an internal layer of refractile cells covered by an 

 external granular layer, but by more careful investigation it is easy 

 to make out that these two apparent layers are merely parts of a 

 single layer of cells. The ciliated cells situated more posteriorly 

 entirely lack the retractile inner portion, and appear granular 

 throughout. They are also slightly broader, and have more convex 

 outer surfaces than the other ciliated cells, forming an equatorial 

 zone of intermediate cells, not very distinct in the living object. The 



* Figs. 1 6 represent the development of L. varialilis, x 1000 diameters. All 

 but 1 and 2 are semidiagrammatic and combined from different preparations. 



