MUCOR MUCEDO. 313 



hydrochloric acid, to remove them just before needed for use, 

 And -wash them in distilled water, which has been boiling for 

 some hours. Glasses cleaned in this way allow the drop of 

 culture-fluid to be well spread out, a point of no small advantage. 

 These precautions are rendered necessary by the existence in the 

 atmosphere of various spores which might infect the culture. 

 It is necessary now to sow a single gonidium, and this is effected 

 in the following way. A gonidangium from a pure culture is 

 transferred with the forceps to a watch-glass filled with boiled 

 water. In this the gonidia will soon become uniformly diffused. 

 A drop of the fluid can then be taken out of the watch-glass by 

 means of a needle which has been disinfected in a flame, and laid 

 in an elongated streak upon an object-slide. This streak is then 

 examined under the microscope. If it contains but one gonidium, 

 it is in a fit state for use for the culture ; but if it contains more 

 than one, a part of it must be wiped off with a scrap of boiled 

 rag. A drop of the culture fluid must then be laid on the goni- 

 dium, the slide then laid upon one of the zinc frames represented 

 in Fig. 1, and this covered with a bell- jar, the edges of which are 

 immersed in water. It is even better to add a few drops of the 

 culture-fluid to the watch-glass of water containing the gonidia, 

 and to leave them there for a few hours. The gonidia swell to a 

 ten-fold size, becoming globular, and are much easier to see and 

 count in the streak upon the object-slide. The swollen gonidium 

 will show a large central vacuole (Fig. 113*, B). 



Several germ-tubes will quickly be developed from the 

 gonidium, will grow rapidly, and, in the course of a day, as 

 can be readily seen by repeated examination under the micro- 

 scope, will produce a much-branched mycelium (Fig. 113*, C). 

 Successive grades of branches progressively diminish in thickness. 

 The entire mycelium is devoid of partition walls, and is filled with 

 dense, granular protoplasmic contents, in which are numerous 

 vacuoles. When the mycelium has attained a definite size, 

 further branching ceases ; the protoplasm becomes more granular 

 and darker, and begins to collect towards the middle of the 

 mycelium. Here the gonidiophore rises out of the fluid as a 

 thicker branch ; and when this has attained a certain size, the 

 end swells into a head (Fig. 113*, C), the bulk of the protoplasm 

 of the mycelium moves towards this rudimentary gonidangium 

 (Fig. 113*, D), and is replaced by cell-sap. The gonidangium 

 is cut off by a partition wall, which bulges into it (E), and its 



