162 Miscellaneoua. 



powers, which may be most judiciously referred to the principle of 

 least resistance, more especially as the smaller auimal-cell which is 

 in advance in division is placed in the wide obtuse pole, and thus is 

 enabled to divide again in the long direction of the oviim. 



The first division, taking place in the longitudinal direction, does 

 not, as further observations show, divide the ovum into the mate- 

 rials for the right and left halves of the body, although subsequently 

 the sagittal plane of the embryo again coincides with the long axis 

 of the ovum. This, however, may also be referred to the least 

 resistance as a guiding principle, seeing that both in the embryo 

 and the egg-capsule the longitudinal exceed the transverse axes in 

 extent. 



The agreement in the position of the directive vesicles, the first 

 divisional plane of the segmenting ovum, and the future long axis 

 of the embryo would consequently have to be referred to a common 

 cause, which interposed as such in each case, but without the first 

 orientation in space being conditional for any of the following ones. 



If it be considered further that the egg-capsule is furnished by 

 the ovum itself, so as the laws laid down by men become a measure 

 and rule of conduct for men, the egg-capsule, although itself without 

 any formative power, becomes in its rigid form the essential regu- 

 lator of the position of the developing embryo of Lepas in the egg. 

 — Sitzunr/shericJite der hon. preuss. Akademie der Wissenschaften zu 

 Berlin, December 8, 1887, pp. 1052-1055. 



On the Infection of a Frog-tadpole by Saprolegnia ferax. 

 By Prof. J. B. Schnetzler. 



In a glass vessel containiug 2 litres of water, in which the oxygen 

 was continiaally renewed by aquatic plants, the author had two 

 frog-tadpoles which had not undergone their transformation since 

 last year (1886). However, the branchiae had disappeared, and the 

 tadpoles came to the surface of the water to respire air. These 

 larvfB were nevertheless very lively, and tbeir dejections proved that 

 nutrition was effected in a normal fashion. As the volume of water 

 and the quantity of food have a marked influence on the develop- 

 ment of the larvoe of frogs, the author removed one of these tadpoles 

 and placed it in a second vessel with aquatic plants. Both vessels 

 were of ordinary white glass. 



The two larvoe remained very lively without undergoing any 

 metamorphosis, until, towards the end of last June, a fly {Sarcopliaga 

 carnaria) was placed in the first vessel. After death its body became 

 covered with white filaments of Saproleynia ferax. The tadpole, 

 which had continued very lively up to this time, now soon became 

 more sluggish in its movements ; its body became quickly covered 

 with filaments of Saprolegnia, and within two days after this infec- 

 tion it was dead. 



Microscopic examination of the Saprolegnia ferax, which covered 

 the body of the fiy, showed that the protoplasm of its filaments was 

 transformed into thousands of zoospores, which, by means of their 

 two vibratile cilia, rapidly diff'used themselves through the water. 

 As these zoospores swim about and thus spread themselves through 



