30 Dr. W. Dybowski on Lubomirskia baicalensis. 



The variability of the sponges in regard to their mor- 

 phology is a generally known fact. That Lubomirskia 

 baicalensis follows this general rule we have a satisfactory 

 proof in the material before ns. 



The morphological variability of Lubomirshia baicalensis 

 has already attracted the attention of Miklucho-Maclay * ; 

 but, as may be concluded from his words [l. c. p. 8), he was 

 acquainted only with inconsiderable variations. In order to 

 furnish as complete a description as possible of the form and 

 structure of our sponge, I will here summarize all that is 

 already known upon the subject, and enlarge it by my own 

 observations. But, remarkable as are the differences in the 

 form of the sponge under consideration, all these morpho- 

 logical deviations may always, by careful investigation, be 

 referred to one and the same type. 



The simplest and therefore typical form of our sponge is 

 that of an arborescent stem with cylindrical erect branches f. 

 The branches originate sometimes at different heights (see 

 Miklucho, I. c), but sometimes at the same level (see Dy- 

 bowski, I. c). 



This simplest form as just described is modified in various 

 ways, and the most important modifications are the fol- 

 lowing : — 



I. Forms lu which the type is distinctly recognizable. 



a. The erect cylindrical branches of the sponge are not free throughout, 



but unite -with one another by several transverse anastomoses of 

 various thickness and length (see Dybowski, L c. p. 12, tab. i. 

 fig. 1). _ 



b. The erect cylindrical branches of the sponge stand so close to each 



other or to the stem that at the surfaces of contact the_y coalesce 

 either with one another or with the main stem. By this means 

 there are formed very variously shaped, elongated, more or le.-s 

 flattened bodies, from the top of which larger or smaller branches 

 originate (see PI. II. tig. 1 b). 



II. Forms in which the type is almost entirely effaced. 



a. Arborescent sponges. 



a. The branches do not stand erect, but form a more or less acute 

 angle with the main stem. The individual branches are not 

 cylindrical, but thinner at the free extremities than at the base. 

 (Specimen in my collection.) 



/3. The short nearly cylindrical branches are pinnately arranged ; but 



* Miklucho-Maclay, " Ueber eiuige Schwiimme des ncirdlichen Stillen 

 Oceans und des Eismeeres," in Mem. de I'Acad. des 8ci. de St. P^tersb. 

 ser. 7, tome xv. no. 3. 



t See Dybowski, /. c. tab. i. fig. 1 ; Miklucho-Maclay, /. c. tab. i. fig. 5 ; 

 and Middeiidorff, ' Sibirische Reise,' Bd. iv. Theil ii. Lief. 1, p. iOOo. 



