W. ZOPF ZUR KENNTNISS DER PHYCOMYCETEN. 117 



like forms, in comparison "witli the fullj-developed plants, were 

 really Ectrogellae, and did not, as might easily have been supposed, 

 belong to another parasite, was proved by the existence of all 

 possible intermediate grades, and will also be put beyond all doubt 

 by the subsequent details of the development. I shall at the same 

 time show that, singularly enough, these colonies of minute forms 

 did not reach the interior of the host-cell by migrating through its 

 investing membrane. As already mentioned, the shape of the 

 freely-developed sac is vermiform ; where room is wanting however, 

 the configuration of the individuals is influenced by conditions of 

 mutual pressure. For instance, the ends of two or more opposed 

 individuals are frequently tapered off by their forcing their way 

 like wedges between the walls of the host and a neighbouring 

 parasite, and this tapering is met with sometimes at one, and 

 sometimes at both poles. The contents of the receptacles at first 

 appear finely-granular, later on it is pervaded by great numbers of 

 closely-packed coarser and highly-refracting corpuscles, so that the 

 sacs form easily-seen objects. One may also frequently observe 

 the formation of vacuoles, which often attain to considerable 

 dimensions. This is not the case, however, in the more robust and 

 lusty individuals, and appears to indicate an abnormal condition of 

 the contents. 



In consequence of its great delicacy no membrane is apparent at 

 first sight. It may be easily demonstrated however by means of 

 staining 1 . 



From the Ancylistic-like condition of the mycelial receptacles, at 

 least in their largest forms, one might expect them to become seg- 

 .mented by partition walls at the beginning of fructification, but 

 this does not occur. Even the longest mycelial sacs form only a 

 single receptacle. The plasma collects after the well-known fashion 

 round the numerous nuclei to form an equal number of swarm- 

 spores. These latter are extremely minute, usually from two to 

 three jx in diameter, rarely more ; they exhibit feeble amoeboid 

 movements, and are provided with a somewhat highly refractive 

 tiny nucleus and a distinct cilium. They escape by excretory 

 ducts, which are, as a rule, already visible as short papillae before 

 the commencement of swarm- spore formation, and which, later on, 

 open by mucous degeneration of their apices. 



The fact of many excretory ducts being formed in the larger 

 sporangia is particularly characteristic of Ectrogella (I have counted 



