REPORT ON THE HEXACTINELLIDA. 25 



Some species undergo multiplication by budding. This process can be studied 

 extremely well in Polyloplms 'philippinensis, where the same specimen frequently exhibits 

 numerous stages in the development of buds, from small papilla-like elevations to 

 adult individuals ready to be separated off (PI. LIV. fig. 1). After the numerous 

 conical protuberances of the lateral surface, which are apically equipped with a 

 tuft of slightly divergent needles, have grown out to a greater length, and have 

 been drawn out into nipple-like structures, they become constricted, and the outer 

 portion expands into a pear-like form. The bud continues to grow gradually larger, 

 expanding especially on its free terminal portion ; a roundish opening is formed 

 at the distal pole, while on the lateral surface a number of conical projecting tufts of 

 needles appear irregularly disposed. The portion connecting the bud with the mother 

 Sponge becomes longer, and at the same time thinner ; finally the union between the 

 two is wholly severed, and the bud thus separated is attached only by a weak bundle of 

 siliceous needles. Strain and friction soon effect complete separation, and the bud at 

 length falls to the ground, where it becomes independently attached by its own tuft of 

 spicules (PL LIV. fig. 1). 



When, in such a process of gemmation, the undeveloped individuals remain attached 

 by an elongated stalk, ramified colonies with terminal individuals result, as for example 

 in Sympagella nux (PI. XXII. fig. 4). 



These young buds are in their young stages admirably suited for investigation, 

 affording a convenient view of the whole organisation of the form in question. This 

 may be illustrated by glancing at fig. 2 on PL LIIL, where a longitudinal section through 

 Poli/lophus philippinensis is represented. The relation of the entire chamber layer to 

 the general canal system and water stream becomes at once distinct. It may be clearly 

 seen that, however much the layer of chambers is folded, it always forms a continuous 

 intermediate layer between the afferent and efferent lacunae or canals, forms in fact a 

 filtering layer, through the pores of which the stream of water has to pass. 



The above gemmation which results from proliferations of the sponge- waU, must be 

 of course distinguished from a formation of colonies very frequent among Dictyonina, 

 which occurs, however, as the result of the folding of the exuberant margin of a cup or 

 tube-like rudiment. The dichotomous or more complex tubes, which frequently exhibit 

 lateral branches, in FaiTea, Eurete, Periphgragella, Myliusia, Sec, result wholly from 

 the folds of the growing portion becoming gradually closed into complete tubes 

 (PL LXXII. fig. 3 ; PL CIII. figs. 1, 2) as may be readily demonstrated from a careful 

 comparison of the different stages in the development of the colony. 



In some cases, as for example in the young specimens of Lanuginella pupa (PL LIII. 

 figs. 4, 5) which were found isolated, I was of the opinion that I had before me very 

 young forms developed from the ovum. I inferred that chiefly from the fact that both 

 the youngest, simply spherical specimen (2 "3 mm. in diameter) (PL LIII. fig. 4), and a 



(ZOOL. CHALL. EXP. — PABT LIII. 1886.) Ggg 4 



