SPONGID^. 41 



times effected by peculiar bodies to which the 

 name of " swarm spores " has been given. These 

 were oval in form ; more pointed at one end than 

 at the other and consisted of three distinct sub- 

 stances ; viz. I, an epithelial cellular envelope; 

 2, a structureless cortical layer ; and 3, an interior 

 spheroidal medullary portion. The latter is re- 

 solvable into an exterior mucoid layer, containing 

 a variable number of " germ granules," embedded 

 in an albuminous substance and associated with 

 numerous minute siliceous spicula. The swarm 

 spores were actively locomotive, swimming ra- 

 pidly about by means of the cilia which were dis- 

 posed in a regular manner over the entire surface 

 of their bodies. After leading a somewhat restless 

 existence for one or two days they sunk to the 

 bottom of the vessel wherein they were confined, 

 to which they soon after began to adhere. The 

 greater number decayed ; a few, however, were 

 observed to expand into a delicate layer consisting 

 of a gelatinous substance in which minute siliceous 

 needles were embedded, and at length, on the 

 20th day, the characteristic Sponge structures 

 made their appearance. 



In addition to the germ-granules contained in 

 the swarm spores, spherical aggregations of the 

 same bodies, in a free condition, were not unfre- 

 quently met with. They were found in all parts of 

 Spongilla, being especially abundant at the base 

 or attached portion of the mass. 



With regard to the natiu:e of the above swarm 

 spores, and the relation which exists between them 

 and the seed-like bodies, much has yet to be 

 learned. Carter asserts that they are merely ciliated 

 forms of the latter, a statement which, however 



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