110 M. E. Hiickel on the Organization of Sponges, 



imposed upon cacli other. Such stratiiied Hag'ellate epithelium 

 occurs, tor examph>, in Tarroina and Clathrina. 



Besides the tla<2;eUate cells, the entoderm of the sponges 

 gives origin only to one product, the ova. Although here, 

 tollowing the exani])le of all authors, I denominate the germ- 

 cells or reproductive cells of the sponges oca, this is not with- 

 out great hesitation. Thus, although I have most carefully 

 examined with the microseo])C lumdreds of Calcispongi^e, I 

 have never succeeded, either in these or in the other s})onges 

 investigated by me, in detecting any trace of fecundating male 

 elements or zoospermia. I have thus become very suspicious 

 of the generally accepted sexual differentiation of the sponges 

 in general. The only accounts of zoospermia in sponges 

 which seem to merit confidence (although they still require 

 confirmation) are those of Lieberkiihn with regard to Sjwngilla. 

 ^Vhat Carter describes as the zoospermia of SpongiUa are, as 

 Lieberkiihn perceived, Infusoria 5 and what Huxley figm'es as 

 the zoospermia of Thetga are very probably vibratile cells. 

 No less doubtful are the filaments which KoUiker describes as 

 the zoospermia of Esperia. Scepticism as to the occurrence 

 of zoospermia in sponges appears the more justifiable because, 

 on the one hand, the detached fiagella of the flagellate cells, 

 which move briskly, may very easily be mistaken for motile 

 seminal filaments, and, on the other, many of the most expe- 

 rienced observers, such as O. Schmidt and l^owerbank, who 

 liave examined microscopically thousands of sponges, have, 

 like myself, sought in vain for male organs of any kind 

 whatever. I regard it, therefore, as most prudent and advisa- 

 ble, for the present, to doubt the sexuality of the sponges. 

 But then the cells subserving reproduction, the germ-cells 

 {gonocyta), must be designated not as sexual eggs (ova), but 

 as asexual germ-cells (sporje). 



I have found the spores or so-called ova, in all sponges 

 investigated by me, to be perfectly naked and destitute of 

 membrane, like the flagellate cells from which they proceed. 

 Throughout I have never found in the sponges examined hy me 

 any trace of a membrane or true cell-membrane on the cells. 

 All sptonge-cells are naked cells without envelopes (gymnocyta). 

 The spores of the Calcispongiae have hitherto been seen only 

 by Lieberkiihn in Sycum ciliatiim, and by KoUiker in Tarrus 

 and Dunstervillia. I have never missed them in any of the 

 mature Calcispongige investigated by me. They are very 

 easily recognized, as they are distinguished at once from the 

 flagellate cells by their very considerable size and the absence 

 of the flagellum, whilst no other independently persistent cells 

 (except these two cell-forms of the entoderm) occur in the body 

 of the Calci-spongise. 



