HARDWICK&S SCIENCE-GOSSIP. 



i95 



the direction of the hurricane was towards the scene 

 of volcanic activity, as if the air were being drawn into 

 the vortex caused by the explosion. A few hours later, 

 the gale as suddenly ceased, and then ashes began to 

 fall, borne northwards by some upper current of air. 

 We have yet to learn how far these atmospheric 

 movements were connected with or independent of 

 the eruption. 



There are some excellent geologists in New 

 Zealand, who have now a rare opportunity of investi- 

 gation. No mud-eruptions at all comparable in 

 magnitude to those of this summer in New Zealand 

 have ever been known. The connection of these 

 with the explosions of Tarawera, the relation of the 

 latter to the lava-reservoir inside, the nature of the 

 so-called "flames" and "pillar of fire" so con- 

 spicuous on the night of the eruption, the sources of 

 the "fire-balls," and many other details, offer a wide 

 and most interesting field for the colonial observers. 

 Geologists all over the world will await with much 

 interest the publication of their investigations. 



Since the above was written, we are told that 

 heavy showers of rain fell, which have washed away 

 much of the ashes. The colonists say that the ashes 

 have proved an excellent top-dressing to the pastures. 



A GROUP OF ROTIFERS. 

 Notes on the Genus Colurus. 



TO the April number of Science-Gossip I com- 

 municated some notes on the genus Euchlanis, 

 family Euchlanidota, and with the Editor's per- 

 mission I now follow with some notes on the genus 

 Colurus, belonging to the same family. Many 

 microscopists seem to have very vague and hazy 

 ideas in reference to the more minute rotifers be- 

 longing to this family, and especially it would seem 

 in regard to the genera Lepadella, Metopidia, and the 

 genus now under consideration. In Science-Gossip 

 for June 1884 I gave a figure and short description 

 of a rotifer since identified as Colurus deflexus, but of 

 the species of which I was then uncertain. In the 

 following number a gentleman who described himself 

 as "a constant student of the rotifers," informed me 

 that my rotifer was a very common one ; and, if I 

 would consult " Pritchard " again, I should find it 

 described under the head of Lepadella. I received 

 private communications from numerous other micro- 

 scopists, referring it either to Lepadella or Meto- 

 pidia ; while, strange to say, not one of them 

 recognised it as undoubtedly belonging to the genus 

 Colurus. Now, whatever imperfections there might 

 have been in my description and figure, yet I clearly 

 described it as having one unmistakable character, 

 viz., the lorica being open on the ventral surface, 

 a peculiarity possessed by no other genus but the 

 one in which I placed it. I fear that the above 



instance is but an exemplification of the fact upon 

 which I commented in my last communication, that 

 too many "constant students of the rotifers" arc 

 satisfied with a merely superficial examination of their 

 captures, and are quite content to identify them with 

 any published figure to which they happen to bear a 

 general resemblance. Such a method, if method it 

 can be called, is not of the slightest scientific value, 

 and is certainly not calculated to increase our know- 

 ledge of these interesting animals, or to assist brother 

 naturalists in any of their difficulties. There is, 

 however, some little excuse for them. Only those 

 who have conscientiously endeavoured to surmount 

 the numerous difficulties attending the identification 

 of some of the more minute free -swimming rotifers 

 can appreciate the perplexities and the amount of 

 labour involved in arriving at a satisfactory result. 

 The Micro. Dictionary affords the student very little 

 assistance, as it gives a description of species in 

 comparatively few instances, and these and its figures 

 are almost invariably transcribed from Pritchard 01 

 other older authorities. Pritchard, while treating 

 more fully of the various species, is yet sometimes 

 very vague in regard to the less frequently recurring 

 forms, and the description he gives is generally in- 

 sufficient, frequently very loose and irregular, and 

 in some cases even is hopelessly inaccurate. In 

 explanation of this we must remember that object- 

 glasses were not so good twenty-five or thirty years 

 ago as they are now ; that illumination was not so 

 well understood ; that observers were comparatively 

 few ; and that the minuteness and almost phenomenal 

 restlessness of these animals all render the study of 

 the Rotifera one of some difficulty, and call forth 

 considerable manipulative skill. It is not sufficient 

 in many instances to study them in one position only : 

 they must be watched, it may be, for hours together, 

 so as to study them in their various aspects, before 

 we can gain an accurate idea even of their outward 

 configuration. One may have an animal under ob- 

 servation, on frequent occasions, throughout the 

 whole summer, and yet there may be one or more 

 aspects of it of which one has failed to get a glimpse. 

 In such a case the only alternative is to study and 

 carefully sketch it in the aspects you do see it, and 

 await a favourable opportunity, perhaps in the next 

 summer, of completing its study. As a general rule 

 the dorsal and ventral aspects are those most frequently 

 seen in rotifers with a depressed lorica, and the 

 dorsal and side aspects of those in which the lorica 

 is compressed. In the genus Colurus, which belongs 

 to the latter class, it is extremely difficult, and 

 frequently impossible, to get a view of the ventral 

 aspect, although it is absolutely necessary to do so— 

 to all at least but an experienced student of these 

 animals — before one can speak positively as to the 

 genus. 



The species of this genus are among the commonest 

 Rotifera in this district (Rossendale), and are found 



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