NATURE AND AFFINITIES OF THE SPONGES. 173 



segmentation, a swarm of unicellular flagellate zooids resembling those 

 from whence they derived their origin. 



The very important phenomenon of spore-production by sponges, com- 

 parable in every way with that exhibited so abundantly among the ordinary 

 Infusoria, and which places in a still more prominent light their close 

 connection with the typical Flagellata and Protozoa generally, has now 

 to be described. While the occurrence of spores in various sponge- 

 types had been noted so long since as the year 1874, its first record was 

 contained in a communication made by the author to the Linnean Society 

 in June 1877 ; further reference to this phenomenon, with accompanying 

 illustrations, being likewise published in the author's " Notes on the Embry- 

 ology of Sponges," contributed to the 'Annals and Magazine of Natural 

 History' for August 1878. Since that time, however, much additional 

 material has been amassed in demonstration of this special mode of repro- 

 duction, and more especially in connection with various sponge forms 

 collected and examined by the author at Teignmouth, Devonshire, in the 

 summer of 1879. 



The types thus recently examined in the living state included more 

 especially Grantia compressa, Grantia (Sycon) ciliatum, Leucosolenia 

 botry aides, and Leucosolenia (Ascettd) coriacea, among the calcareous 

 forms, and Halichondria punicea, H. incrustans, and a species of Esperia 

 belonging to the siliceous series. All of these were found to yield 

 sporular bodies in abundance, their most profuse development being, 

 however, afforded by the calcareous type Leucosolenia coriacea. Here 

 symmetrically rounded masses, irregular patches, or more or less isolated 

 spores, of a yellow or light brown hue, were found scattered literally in 

 thousands throughout the substance of the cytoblastema and in various 

 stages of development. In their earliest observed condition, in which the 

 spore-aggregations form compact spheroidal masses, these masses mea- 

 sured in diameter the i-i3OOth, and the individual spores that only of the 

 i-75OOth, part of an English inch. Bringing to bear upon them the high 

 magnifying power of 2500 diameters, as obtained with a -^-'mch objective 

 by Powell and Lealand, it was discovered that at a very early period of 

 their development, that is in all that had arrived at twice their first 

 noted bulk, each spore possessed a single long vibratile flagellum, and 

 corresponded precisely in aspect with the initial phases of many of the 

 simple monad types hereafter figured and described. Moreover, as 

 liberated by dissection from their natural position in the cytoblastema of 

 the parent sponge, these sporular bodies, with their vibrating flagella, 

 were set free in the surrounding water singly, in twos or threes, or in 

 larger social aggregations that singularly resembled the early phases of 

 development of Monas (Heteromita] lens, described at page 137, and 

 delineated at PI. XL Figs. 8-13. Not unfrequently, again, these motile 

 spore-aggregations were of considerably larger size, and retained their 

 primitive spheroidal form. Illustrations of all of these various conditions 



