THE HELIOZOA 29 



is mitotic, and is probably of the type observed in adult Actino- 

 sphaerium or of that seen in Acanthocystis, according to the presence 

 or absence of a permanent centrosome. 



Budding has been observed in several cases ; and the process 

 has lately been described in detail by Schaudinn (19) in Acantho- 

 cystis. The nucleus divides directly once or several times, so that 

 the body may contain a considerable number of nuclei; during 

 this process the pseudopodia are not withdrawn, the centrosome 

 and the system of axial filaments remaining unchanged. One of 

 the nuclei resulting from this division remains in the body of the 

 parent without further change ; each of the others travels into a 

 small projection from the surface of the body, which is the future 

 bud. Every bud is covered with a layer of spicules derived from 

 the parental skeleton, but it contains no centrosome, nor any trace 

 of radial fibres. The buds so formed may behave very differently 

 in different cases, and there is at present no knowledge of the 

 circumstances which determine their behaviour. A bud may 

 separate from the parent in the condition described, and may 

 divide one or more times, the products of division going through a 

 short resting stage before emitting pseudopodia; or the resting 

 stage may occur immediately after the bud leaves the parent, in 

 which case it does not divide before assuming the adult condition. 

 In these cases there is nothing like " spore-formation " ; but a bud 

 may become amoeboid, and creep out of its skeletal investment, 

 either before the skeleton has separated from the parent or 

 immediately afterwards ; and such an amoebula may creep about 

 for a day or two, by means of blunt pseudopodia, before it becomes 

 spherical and secretes new spicules ; or, division of the nucleus may 

 occur within the bud, so that several amoebulae leave it, instead of 

 one. Lastly, an amoebula, at the moment of leaving the parental 

 skeleton or soon afterwards, may develop two flagella, by means of 

 which it swims for a short time; such " flagellulae " quickly 

 become amoeboid and creep about for a further period as amoe- 

 bulae, before becoming spherical. None of these buds or spores are 

 known to conjugate, and indeed the origin of sexual spores by an 

 amitotic division would be remarkable ; but, however they behave in 

 the meantime, about the fourth or fifth day after emission each of 

 them becomes spheroidal, and secretes a skeleton of small tangential 

 spicules, which are first formed in the immediate neighbourhood of 

 the nucleus, and afterwards travel to the periphery. The centro- 

 some arises from the nucleus (Part I. Fasc. II. Fig. 20, p. 41), and 

 after it is established the axes of the radial pseudopodia appear. 



The formation of " swarm -spores " was first described by 

 Cienkowski (4) in Clathrulina ; it was more recently discovered by 

 Schaudinn (19) in Acanthocystis] and it may occur in Actinophrys 

 (Penard). 



