404 M. N. Lieberkiihn on the Development of 



These rows of rods project slightly outwards beyond the surface 

 of the sponge, and are further connected with each other by 

 groups of needles. The distance they are apart from each 

 other is easily recognized in a branched sponge which has 

 been kept out of the water for a short time; the apices of the 

 rods project strikingly, and render the surface of the sponge 

 spinous. Each projecting point is seen under the microscope to 

 consist of a bundle of several needles. 



The gelatinous substance has been examined most accurately 

 by Dujardin. Small portions exhibit under the microscope 

 Amoeba-like movements; but whether these are vital phaeno- 

 mena, as supposed by Dujardin, or are connected with decay, is 

 unknown. Other portions were furnished upon part of their 

 surface with long cilia, by means of which they rapidly changed 

 their position, at the same time emitting processes from the por- 

 tion free from cilia, and again retracting them, just like Amoebae. 

 The ciliated portions were not found in winter, but appeared in 

 the spring ; in the winter, only those exhibiting the Amoeba-like 

 movements were present. These portions, which are always 

 obtained by spreading living Spongillse upon an object-glass, 

 are not, however, amorphous masses, as represented by Dujardin, 

 but frequently exhibit distinct structures having the form of a 

 cell : this is especially observed in winter, when the granular 

 matter is not. so abundant. When the Amoeba-like movements 

 cease in one of these masses, a nucleus and a nucleolus become 

 visible ; and at this time, not merely a part of the gelatinous 

 mass consists of them, but the entire sponge. 



I have never succeeded in displaying the cell-membrane itself; 

 hence the use of the term ' cell ' is not at present justifiable, being 

 used for the sake of brevity. Sometimes the nucleus with its 

 nucleolus is found isolated between other uninjured cells, espe- 

 cially when the sponge is not perfectly fresh. The cells are 

 Y-^Q-^ inch in diameter, the nucleus ^joo> ^^^ nucleolus gjjVcj* 

 Frequently the nucleolus only is visible in the cells, and some- 

 times not even this, the interior of the globule being then filled 

 with green or colourless granules. Frequently also the cells 

 do not attain the above magnitude. In some cases I found 

 structures containing within them foreign bodies, such as Dia- 

 tomacese ; in other respects these exactly resembled the sponge- 

 cells, containing also a similar nucleolus; a contractile vesicle 

 wasabsent; they emitted and retracted processes, and were pos- 

 sibly true Amoebae, in which often no trace of a contractile vesicle 

 can be detected. True Amoebae with contractile vesicles are not 

 rare in sponges. 



The Spongillae generally abound with infusorial life, especially 

 in winter. I found, in the course of last winter, large numbers 



