Pectinatella 



WHOLEMOUNTS IN RESINOUS MEDIA 



61 



attraction of a drop of water. The speci- 

 men is taken from the water with a large 

 ej^e-dropper type of pipet and placed in a 

 considerable volume of water on the slide. 

 It is then easy to arrange the parts with 

 needles; but it is difficult to lower a second 

 slide on top of the first without disarrang- 

 ing these parts. An alternative method is 

 to place the shde with its coverslips in the 

 fingerbowl with the specimen, to arrange 

 its parts under water and to place the 

 second sUde on top. Whichever process is 

 adopted, the slides are then tied or clipped, 

 together and transferred to a jar of 95% 

 alcohol, where they may remain for a 

 week, or until next required. Each speci- 

 men is treated in this manner; and it is 

 better not to try to flatten two or three 

 specimens on one slide. 



When it is desired to continue mounting 

 the specimens, each slide is taken and 

 placed in a fingerbowl of 95 % alcohol be- 

 fore the cords which bind them together 

 are cut, or the clips removed. Getting the 

 two sUdes apart without damaging the 

 specimen is not easy, particularly if the 

 specimen tends to stick to one or the other 

 of the sfides. The simplest method is to in- 

 sert the blade of a scalpel into the gap 

 between the shdes and, twisting it slightly 

 sideways, see if the specimen is free. If the 

 specimen shows signs of sticking to one 

 slide, the other may be removed and the 

 specimen washed from the shde to which 

 it is stuck with a jet of 95 % alcohol from a 

 pipet. If it shows signs of sticking to both 

 shdes, it is still possible, bj' projecting a 

 jet of 95% alcohol between them, to free 

 it from both. Each shde is treated in due 

 order until one has accumulated the whole 

 of the flattened specimens in a dish of 

 95% alcohol. It must be understood that 

 these specimens have been hardened flat 

 so that no amount of subsequent treat- 

 ment will ever swell them out again or 

 prevent them from remaining in the re- 

 quired position. 



It is recommended, if there are several 

 specimens to handle, that a series of the 

 Uttle cloth-ended tubes shown in Fig. 23 

 be used. The only alternative is to handle 

 each specimen with the aid of a section 

 lifter with the consequent risk of damage. 

 Though not nearly so satisfactory, it is 

 also possible, at least for the process of 



staining and dehydration, to place the 

 specimens all together in a small vial in 

 which the different fluids used may be suc- 

 cessively placed. 



A wholemount of this type is best 

 stained in carmine and the choice would 

 lie between Mayer's carmalum (a detailed 

 description of the use of which is given in 

 Chapter 20), Grenadier's borax-carmine 

 (also described in Chapter 20), and May- 

 er's paracarmine, which will accordingly 

 be selected. Preparation of this stain (the 

 formula for which is given in Chapter 20 

 under the heading DS 11.22 Mayer 1892) 

 does not present any difficulty, but it 

 should be noted that the differentiating 

 solution is 0.2% solution of strontium 

 chloride in 70% alcohol. Adequate sup- 

 plies of this should be available before one 

 starts staining. 



The specimens are passed from 95% al- 

 cohol to 70% alcohol. They will naturally 

 float, but as soon as they have sunk to the 

 bottom it may be presumed that they are 

 sufficiently rehydrated and either the 

 cloth-ended tube containing them may be 

 transferred to the dish of stain or the 70 % 

 alcohol may be poured out of the tube and 

 stain substituted for it. One of the advan- 

 tages of this stain is that it is relatively 

 rapid in action — very few specimens will 

 not be adequately stained in five to ten 

 minutes — but it does not matter how long 

 the materials remain in it. It is, therefore, 

 often convenient to leave the specimens in 

 overnight and to start differentiation the 

 next morning. They are then either re- 

 moved to the differentiating solution or, 

 alternatively, the stain is poured off and 

 the differentiating solution substituted for 

 it. In the latter case three or four changes 

 will be required, owing to the necessity of 

 leaving some stain in the bottom of the 

 tube to avoid pouring the specimens out 

 with it. Unless the operator is quite ex- 

 perienced, it is safer to shake the tube so 

 as to distribute the specimens thoroughly 

 in the stain, and then to tip this into a 

 large fingerbowl of dilferentiating solution 

 from which the specimens may be subse- 

 quently picked out and transferred to a 

 new tube of differentiator. It is tragically 

 easy, in pouring off stain, to pour speci- 

 mens with it down the sink. As soon as the 

 stain has been washed off with the dif- 



