86 General Notes. (January, 
Tscherniawsky commonly found in the Black sea very large stones 
which were perforated like a sieve by colonies of Clione; these | 
worked in conjunction with numerous boring Nemertine worms, 
annelids and bivalves, so that the durability of stone piers, wharves | 
and other marine structures was impaired. “i 
The question then arises how the Clione bores its way into the | 
hard calcareous structure. Does it go onina chemical or me- 
chanical way, or does the sponge simply settle itself in passages | 
previously bored by other animals? We must, he says, consid 
a prion that the parasite sponges are supplied for this purpo 
with special means or facilities which are wanting in the free-liv- | 
ing sponges. Hence arises the second question: How has the | ’ 
parasitic mode of life expressed itself in the structure of the body: | 
Nassonow set himself to the task of answering these inquiries. | 
light. : 
k 
- On June ttth he noticed a number of embryo sponges which 
vei could observe the operations of the sponge by transmittee 
sponge begins its work of destruction. At first it appears as $ 
rosette-like mark. The sponge sends out fine offshoots into the 
e S 
grown sponge, with all its branches and galleries, occupying 
very considerable surface, is naturally very great. 
1 The sponge bores its passages, in all probability, by secreting an acid. 127 
tect the presence of the acid would be difficult on em of the cone alkaline 1® 
action ot the sea water. Pee 
