or Mother Cell of the Spicule, 101 



The result of my observations may be found in the paper to 

 which I have alluded ; and at p. 23 (' Annals/ I. c.) , on the 

 development of the spicule, I have thus expressed myself: — 



" At the earliest period that a spicule becomes visible it 

 appears under a hair-like form of immeasurable thinness, and 

 enclosed in a sponge-cell of a spindle-shape, which has 

 assumed this figure to accommodate it. The nucleus of the 

 cell is now seen in its centre, and the spicule, about l-400th 

 of an inch in length, lying across it (fig. 8, a'), &c." 



It will be seen by the form of the figures that both 

 Lieberkuhn's and my own observations had reference to the 

 skeleton-s^icules, viz. those spicules which are essentially 

 connected with the horny fibre of the sponge, in contradistinc- 

 tion to those minuter forms which are essentially connected 

 with the sarcode, for which I have lately proposed the name 

 of "^esA-spicules." 



Let us now see how far later observations have confirmed, 

 these views in the latter. 



In a copy of a report on the siliceous sponges of the North 

 Sea collected during the German expedition of 1871, kindly 

 forwarded to me by the author (Dr. 0. Schmidt) in July 1873, 

 my attention is directed to a part where he states that the 

 anchorates and bihamates of an Esperia were observed to 

 originate in genuine cells. " An einer bei Arendal vorkom- 

 menden Esperia habe ich nun die sehr interessante Entdeckung 

 gemacht, das sowohl die Spangen als die Haken aus einem Ver- 

 kieselungsprocess von Zellmembranen oder wenigstens der 

 membranahnlichen Oberflachenschicht von echten Zellen her- 

 vorgehen, &c." (p. 431). 



This I have just now been able to confirm in Halichondria 

 cegagropila, Johnston (Brit. Sponges, p. 119, and type spe- 

 cimen in Johnstonian collection, British Museum), the common 

 Esperia here (Budleigh-Salterton, Devon). It is desirable, 

 however, before going further, to give the diagnosis of what 

 I have arranged in the British Museum under the head of 

 " Esperiadae." Briefly this consists in the presence of one 

 kind of skeleton-spicule only, and an anchorate which is gene- 

 rally inequi-ended (PL X. fig. 12, a, b) ; while Schmidt would 

 almost as strictly confine his " Desmacidinas " to the presence 

 of the tricurvate (Bogen). Still, how far groups or species of 

 sponges may be determined by the " flesh-spicule" remains to 

 be seen, since in many, otherwise widely different, I have ob- 

 served the same form of flesh-spicule, almost, too, as if the 

 latter prevailed in certain localities. 



But to return to our subject : the specimen of Esperia to 

 which I have alluded was charged with four kinds of cells, 



